Most of us can probably agree that has played Star Fox 64 that Slippy was a little on the annoying side and the game might have been slightly better if he wasn't included or had a different attitude.  In Star Wars Episode 1: The Phantom Menace who is the first character you think of?  I always think about Jar Jar Binks and how I found him very annoying in every scene he was in.  This didn't make me despise the movie or despise Star Fox for having Slippy but it was a minor set back.  

If character design is done right you begin to care about certain people you may meet or characters that travel with you throughout the game.  In the case of Star Fox again, I never really cared when Slippy was in trouble because that would just mean he would go back to the Great Fox for repairs and I wouldn't have to hear his jabbering for the remaining of the level but if it was Falco in trouble; everything was halted and the main objective was to help him out.

Character design and interaction is more important in Role-Playing Games though because if you're going to have someone follow your character around all game, they need to have good interaction with the player so it doesn't feel like a rock is following you. They need to have some sort of back story to keep you interested in them and for the player to want them with you in your adventure. Mass Effect did a great job at character design as well, for your other party members.  

Depending on who you took with you on a quest would sometimes dictate how the quest would play out.  Sometimes if you brought Wrex (a big burley bounty hunter alien) with you to go assasinate or make peace with someone Wrex would have special interactions with the target and might actually persuade you to shoot this guy instead of make amends.  Making good or evil decisons was a big factor in Mass Effect and sometimes it was influenced by your party members and how you interacted with them.  Star Wars: Knights of the did this well too; making light side or dark side decisions.  When you turned out to be really dark side oriented you even turned against some of your former party members which made the game really interesting and different. What other game gives you the decision to kill your own party members!?  

More on the design aspect of things. If you have this large breathing world with different species living amongst each other it should be believable to the setting of the game.  If the setting is back in the Jurrassic Period it wouldn't be very believable to see robots walking around unless it was part of the game (sounds like an interesting idea for a game to me).  The real point is it's nice to have some slight sense of how each character interacts with the world.  When it's dark you may see animals or characters go to sleep and when it's the morning they'll come out and greet the morning air.  You witness one towns member trading with a certain guy everyday in another town so you should be able to get some insight as to the relationship between these trading towns and the people to immerse yourself deeper in the game.

Character design and interaction is just as important as any other part because a game would be pretty boring if it was just you (the player) running around alone, everyone said the same dialogue and acted similar to the last guy you talked to.

Replay value is a very important factor in creating and playing a video game.  You don't want your players to just play it once and throw it in the used games pile never to be played again. Games should be able to be played many times and at least have something new each time.  

A lot of games being recently released are having more and more replay value to their games aside from just multiplayer.  Achievements within the game always make the perfectionists (like myself) work hard at the game to get every achievement and unlockable.  In my opinion though, having a game with multiple endings always has the best replay value.  Anybody remember Chrono Trigger? If I remember right it had about 8 different endings you could get. Different endings are always the most rewarding  to learn more about the story and see what the result is if you did something different earlier in game. Getting an unlockable for beating the game on a harder difficulty is not only a good idea but a great challenge for gamers which includes some well earned bragging rights.  

Some games have a good guy/ bad guy ending which is ok for having different endings but it can probably be assumed how it's going to end.  If you played as the good guy and everyone is saved in the land and replay it to play a bad guy you could probably assume not everyone is going to be saved.  

Multiplayer is a great addition to games to add replay value but isn't necessarily always needed.  It's even better when unlockables from the single player can be used in the multiplayer mode like Rainbow Six Vegas 2 did.  In case you don't want to play online you can play through single player and earn achievements as well as new gear for your character.  It was well planned out and should be considered in other future games.  

I don't know what happened with that previous post but it got shortened down.  Here's the real blog post.

The other blog posts about the Ultimate Game have all been small details that enhance the game but the main idea that makes or breaks the game is the gameplay itself.  You can have the coolest sounding game and the coolest sword peripheral but if all you have to do is swing it back and forth to make it through the entire game, it's going to get bland fast.  Many action games have fallen into the bland category with intricate combos you can pull on your enemies and flip around and look cool but in the end you can just click "A" three times for the basic punch-punch-kick combo and beat every opponent you come across.  Other games become one sided because of a special move or powers your character can do like slowing down time, super powers or super health, ultimately ending in boring gameplay after the second level.  If done right these player enhancements can be done right.

Crysis gives the players enhanced abilities like super strength, cloak and speed.  The game has set limits on each of these powers so the player can't exploit it and use them entirely through the game.  The Matrix or Max Payne set limits on slowing down time which brought some balance to the game so the player wasn’t so overpowered and kept the game challenging.

Some games have been known to try and sell a game on licensing for a superhero and make it look totally awesome but if all you are really doing is flying through rings in the air as Superman no one is really going to feel as cool as him (Superman 64).  In most Spiderman games, swinging around may be really fun but when it gets down and dirty fighting enemies it becomes very clunky almost as if the developers focused most of their attention on the freedom of swinging around.

Gameplay brings everything together to hopefully make the best game you've ever played.  It's important to keep the level of difficulty maintained, keep limits on player powers and keep the player engrossed in the story and combat so it's not just press “A” the entire way through to win.

Art direction is not only appealing to the player to see when they check out the game, it is also a nice change from the usual "realistic" graphics. 

Legend of Zelda: The Wind Waker shocked and awed players when they saw the game take a cel-shaded approach rather than a realistic approach that teased us all when the game was first rumored. Some fans were offended by the choice of cel-shading but once they experienced the game most were blown away because it seemed to fit so well in the game. You can see the wind wisp by as you sail the open sea watching the ocean waves curl around your boat, it was simply amazing, not to mention an amazing game.

Okami was another that had an excellent and new art style. The game seemed like it was straight from an ancient water coloring book. Vibrant colors surround the wolf protagonist as he runs by lush green meadows, soft pink flowers and as you draw with your paintbrush colors burst out at you initiating attacks, create gusts of wind, draw bombs and other various tasks. It’s truly a beautiful game and definitely brought something new to the gaming world.

Don't get me wrong, realistic games are also nice. How far the gaming world has come in graphics from the 8-bit Mario is astounding and should be displayed. In Legend of Zelda: Twilight Princess the game went for the realistic approach but still had some effects from Wind Waker; how the smoke plumed and a hint of cel-shading was displayed when Link was in the dark world as a wolf.

Art direction is important in a game to keep things new just as innovation. I'd like to see more games that switch different art styles during gameplay to keep new levels/worlds new and interesting.