After 5 years of using the same Pentium 4 PC, I am finally getting an upgrade this week. 
I have an Xbox 360 so I have been mostly playing that since 2006, although most of the games I played were 360 or console exclusives. I am wondering what games must I play that have come out since 2006 or so? 
 
I have always enjoyed pc gaming and I'm looking forward to getting back playing more games on it, especially since we have got to the point where games on the pc run smoother and look nicer than their console counterparts.  
I'm interested in all genres and even games that I have already played on the 360, since I'm sure I'd enjoy playing through them again with a couple of mods thrown in.

If you're looking for great multiplayer, get Battlefield: Bad Company 2. Its PC community is especially big.  Another good one to get is Dawn of War II if you're into RTS. You can also alternatively wait for Starcraft II's release this year (granted that Mike Morhaime of Blizzard keeps his word that its releasing this year).

what are the specs of your upgrade? if it means you are getting a 5000 series card and an i7 i would suggest buying Arma 2 for realistic tactical combat and dawn of war 2 if you are into strategy.

I'm getting an i5-750,  an HD5770 GPU and 4GB of RAM. Should be enough to run everything, I'm not a person who needs a ridiculous resolution or lots of AA, so this build should be enough for me. Thanks for the suggestions :)  
Anyone have any other games that they particularly enjoyed in the last few years?

" I'm getting an i5-750 and an HD5770 GPU with 4GB of RAM. Should be enough to run everything, I'm not a person who needs a ridiculous resolution or lots of AA, so this build should be enough for me. Thanks for the suggestions :)  Anyone have any other games that they particularly enjoyed in the last few years? "

Get the Orange Box at the very least.
SupCom 1 & Forged Alliance ; Great RTS games.

" @Joru said:

" I'm getting an i5-750 and an HD5770 GPU with 4GB of RAM. Should be enough to run everything, I'm not a person who needs a ridiculous resolution or lots of AA, so this build should be enough for me. Thanks for the suggestions :)  Anyone have any other games that they particularly enjoyed in the last few years? "

I have (had more like, I upgraded more) a system with specs similar to that other than I had an AMD Phenom II X4 3.4 Ghz processor and it happily ran basically anything on the market today for games.  Most maxed with at least some anti-aliasing at 1920x1080.  You should be fine.  Get S.T.A.L.K.E.R or Empire: Total War.  They're both tons of fun and will run maxed on your system.  Also: Bad Company 2.  It should run on high quite easily and it looks fantastic. "

get just cause 2; it's on the consoles but the modding scene for that game is fantastic.

"yeah i forgot to mention this, even if its got bugs S.T.A.L.K.E.R. Shadow of Chernobyl is one game you should play as its one of the best PC experiences I've had so far. But be sure to get the latest mod for it to lessen the bugs in it. Great atmospheric design that game. :D "

" @VanderSEXXX said:

"yeah i forgot to mention this, even if its got bugs S.T.A.L.K.E.R. Shadow of Chernobyl is one game you should play as its one of the best PC experiences I've had so far. But be sure to get the latest mod for it to lessen the bugs in it. Great atmospheric design that game. :D "

Indeed, I already have Stalker, just never played very much due to performance issues. But I really like games like it, because they're just something very interesting and things you just don't get on consoles. "

Battlefield Bad Company 2 and Dawn of War 2 make for great multiplayer experiences, and there's just countless single player offerings. Dragon Age and Mass Effect 2 are of course very good, and you can try out some indie titles such as World of Goo or Mount and Blade as well.

Witcher and Mount and Blade(And Warband!)

Crysis, just because it's an accomplishment to finally run the game at full settings.

I'm in the same boat, though I didn't order a machine that will run Crysis full spec.  
 
What is out that's awesome that's NOT on a console (because i'm very invested in my PS3s and 360s) 
 
I definitely can't wait to play the Witcher, but what else is killer out there?

Battlefield Bad Company 2 is THE game to get for PC multiplayer gaming right now.  
If you want a single player game that strains your PC's ability to run it try Metro 2033.  
Open world single player game? Get Stalker: Call of Pripyat 
 
RTS? Try to get your hands on Starcraft 2 Beta (pray you get accepted), if not then Dawn of War 2 & its recent expansion "Chaos Rising"

for pc only games i reccomend 
 
torchlight  (fun hack and slash time killer)
civilization 4 (great strategy game)
counter strike (sue me its the best balanced competitve multiplayer game, 1.6 or source) 
mount and blade warband (good slow placed meele combat game)

Well if you don't mind replaying games that you might have on a console, yet get better graphics and a different control interface. I would recommend mass effect 2, resident evil 5 and dragon age orgins. They look fantastic too compared to the console version, you wouldn't belive it. Of course you need a higher rez display to show the graphics.

dragon age origins.

" dragon age origins. "

If you're man enough for it, The Sims 2 and 3 and definitely get Dragon Age:Origins. I also find Fallout 3 to be better on the PC, get it if you don't have it.

grab the orange box right away.  for singe player games, i recommend dragon age, mass effect 2, the bioshocks, dead space, and fallout 3.  for multiplayer games, i recommend league of legends (has a free model), heroes of newerth, starcraft 2 beta (have to preorder or receive a key via opt-in), dawn of war 2, and left 4 dead 2.

"

Well if you don't mind replaying games that you might have on a console, yet get better graphics and a different control interface. I would recommend mass effect 2, resident evil 5 and dragon age orgins. They look fantastic too compared to the console version, you wouldn't belive it. Of course you need a higher rez display to show the graphics.

"

Sam and Max 

I think you should also get Steam as they have pretty much all PC games and huge discounts on the games every week.

#1. Crysis
 #2. Half-Life2
#3. Metro 2033
#4. Dragon Age Origins.
#5. The Witcher
#6. Team Fortress 2
#7. Painkiller
#8. BFBC2

It's also a good idea to use this site.
 
 http://cyri.systemrequirementslab.com/CYRI/

Team Fortress 2   
Heroes of Newerth (or League of Legends if you're new to the genre) 
Company of Heroes