inFamous

Pros

• Combat is exciting, both to look at and participate in.
• Assassins Creedesque climbing abilities make getting around the city a lot of fun.
• Well told story, one that you'll want to play through at least twice so you can see both sides of it.
• Collectibles show up on your mini map, so getting all that crap that would be painful in other games is done with relative ease in inFamous.

Cons

• Some of the side missions aren't really.... Fun.
• Theres no reward for being neutral. Be fully good you get bad ass powers. Be evil you get bad ass powers. If you try to maintain a balance you'll just be hindering your characters growth in the long run.
  

So you're this messenger dude. You unknowingly have this doodad that explodes and kills a tonne of innocent people. Except you. It gives you mastery over electricity.
Throughout the games story you'll learn why exactly you've received these powers and you get to decide what you'll do with them. Whether you'll use them to protect the cities inhabitants from those that would do them harm or whether you'll be the one doing said harm.
And harming is fun.

Your powers follow basic shooter archetypes which I don't feel is especially creative of them, but I don't know what I would've done differently in that regard, hence why I haven't listed it as being a con. I mean what else do you do with it?
You have a power that is essentially a sniper rifle.
You have one that's a rocket launcher. You have grenades.
Unlike some games where you'll often get the feel of just one weapon and happily clutch that throughout the entire play through I feel all of the powers you acquire in inFamous have their uses and it's really good to be able to use your full range of powers and NOT feel like you're hindering yourself by NOT adhering to this one power that is obviously better.
Variety is the spice of life here.

Most of the powers have upgrades. You upgrade by acquiring XP.
Which you get from doing missions, side quests, finding collectibles (I think) and probably a few other stuff that's just not springing to mind right now.
And the upgrades you'll get is mostly determined by your alignment.
Good characters get powers that generally minimize civilian casualties whereas evil characters get massive, explosion causing powers that will annihilate everything you hit. It's fun!

You'll get around the city via a climbing/free running system not too dissimilar from that of say Assassins Creed. Your character tends to gravitate naturally towards grabbable, walkable, climbable things so you'll seldom actually fall and make an ass of yourself. It can feel a little unwieldy to begin with but after a couple of hours you'll be leaping along the sides of buildings, gliding very speed, grace and precision and grinding along the train tracks/power lines, effectively getting you everywhere you'll need to go in a short amount of time.
I've heard some folk lament the lack of some sort of fast travel which makes me somewhat lament the laziness of some folk. It'd be more convenient sure, but then you'll miss out on all the free running, climbing and jumping action and in my opinion that's one of the games strongest points.

My first main objection in this game is that some of the side missions aren't really fun.
In fact most of them are just shortened versions of story progressing missions, which feels like something of a cheat.

My second objection is that there is no reward for being neutral.
Be good and you get awesome powers, be evil you get awesome powers but if you try to maintain a balance your pretty much just limiting your character in terms of the abilities you'll be able to acquire. The world of inFamous is apparently one of blacks and whites, there is no moral grey areas. There is just a right and wrong. I kind of feel like nowadays games with moral choices have actually started to offer choices beyond simple be good and help old ladies across the street or be bad and set fire to a box of puppies. Theres grey areas and I feel that's how it should be.

Those objections however are really minor and don't detract from the game at all.
It looks great, sounds great and plays great and it's really worth at least giving the demo a try and seeing for yourself. There are far worse ways to spend your time.