I'm a bit less into achievements these days, but I'm still quite the completionist. I also have less time for gaming lately.  On that note, what are the easiest Live Arcade games to S-Rank (meaning complete, getting the full 200 pts).  
 
I'll start it off with the easiest for me so far to get the full 200: 
 
Dash of  Destruction (by far the easiest) 
Galaga  
Ms. Pacman 
Pacman C.E. 
Carcassone (best have a friend help with this one)
Uno 
Zombia Apocalypse (easy, but time consuming)
 

Both Banjoa XBLA games are easy, but take some time to get.

Both Sam and Max seasons and Secret of Monkey Island: SE are pretty easy.

Aegis Wing is free, and with multiplayer, it's not that tough.

Battlefield 1943. 

I think you guys should be qualifying 'easy' versus 'time consuming' or 'easy if you have mad skillz'.
 
I found Omega Five's S Rank really easy, but some of those are rares.  BF1943 is really time consuming...

@jakob187 said:

"Aegis Wing is free, and with multiplayer, it's not that tough. "

I gave up on Aegis Wing.  I have everything but the Ace Achievement (score 185,000).  That was nigh impossible...

Any of TellTales XBLA games have easy #S Ranks: Sam and Max / Wallace and Gromit

1 vs 100

Shadow Complex is pretty easy although getting to Level 50 can be a bit time consuming.

I thought The MAW was easy enough and fun.

If you look on my list of S-Ranks you'll probably find a few. 
 

• Golden Axe is easy. You can cheat by changing the settings.
• Bomberman Live isn't too bad.
• Soul Calibur isn't the easiest, but relatively easy if you are familiar with the franchise.
• Spyglass Board Games.

"If you look on my list of S-Ranks you'll probably find a few. 
 

• Golden Axe is easy. You can cheat by changing the settings.
• Bomberman Live isn't too bad.
• Soul Calibur isn't the easiest, but relatively easy if you are familiar with the franchise.
• Spyglass Board Games.

 
Y'know. Whatever. I would suggest wasting your money elsewhere and buy a real game.

"

" Both Banjoa XBLA games are easy, but take some time to get. "

"1 vs 100 "

" @TooWalrus: True.  I've been playing Tooie lately and it's been tons of fun. "

"I thought The MAW was easy enough and fun. "

That Doritos game can be completed in like...3 levels.

Sonic 3 is ridicueasy.

Easiest ones for me (S rank within a couple of hours...) are:
 
- Any of the Sonic Games
-Gunstar Heroes (probably deserves the prize for easiest XBLA game to 200. Basically, you'll have the full 200 upon completing the game, as the non-story related stuff is extremely easy and will probably be completed accidentally).
- Shadow Complex.
-Castlevania: Symphony of the Night

Symphony of the Night isn't terribly hard to do.

"Battlefield 1943.  "

" Shadow Complex is pretty easy although getting to Level 50 can be a bit time consuming. "

" Symphony of the Night isn't terribly hard to do. "

N+ 
Trials HD 
:P

I found After Burner Climax easy S rank

Castlevania SOTN is ridiculously easy, and ridiculously fun.

Case Zero. Monday Night Combat can be boosted.

" Battlefield 1943.  "

The Last Airbender is meant to be really easy for S rank

Age of Booty is an easy 200 if you don't suck at hex based RTS'. 
South Park Lets Go Tower Defence play can be done fairly fast solo, even easier with 1 or more other dudes
Shadow Complex is a great game, and the achievements aren't super though. They'll take a few hours thought, but you'll in no way bore yourself to death.

cloning clyde, SOTN and UNO

Dead Rising 2 Case Zero was way easy for me, Monkey Island 2 should be easy if you know your way around that game.

Dead Rising 2 Case Zero was very easy and you can do everything in 2 runs. I've heard of someone doing everything in 1 run but spending $100,000 in the shop is a pain for 1 run. Shadow Complex is a great game and not to hard to get the 200 Gamerscore.   Dash of Destruction was silly but super easy.

" @Daryl said:

"Battlefield 1943.  "

But very time consuming to get that win 100 games trophy/achievement. "

I'm surprised no one has said Cloning Clyde. Not only is it a fantastic game (I totally want a sequel) but it's super easy to get all the achievements. Which is why I'm surprised that half the achievements are considered "uncommon" here on GiantBomb.

Geometry Wars 2

Wallace and Gromit...800 points for all 4 and it takes about an hour or two to finish each one as long as you have a good guide.

Geometry Wars: RE only took me three years to S Rank. Give it a shot!

Deathspank is an easy S, took me about 4ish hours to 100% the game, so not especially hard, but the get to level 20 achievement can be a bit of a grind (I had done all side quests and only had to defeat the last boss and was still only level 19) 

Afterburner Climax is VERY easy to S rank.  After you play the game for a little while, you unlock a cheat mode where you can make the game far easier, and the settings don't affect achievements.  Should take two or three hours, at most.

My XBLA S-Ranks are in order of easiest are:  
 
Dead Rising 2: Case Zero  
Monkey Island SE 
Monkey Island 2 SE 
Deathspank 
Pac-Man CE

Toy Soldiers isn't terribly hard if you have a guide walking you through some of the trickier things to pull off. Plus it's an amazing game.

" Battlefield 1943.  "