Getting a 360 - What games?

[Hexadecimal16]

BF: BC is ridiculously fun on XBL. Ridiculously fun. The concept of Gold Rush is pretty simple but blowing the crap out of nearly everything conceivable never gets old.

 

[walker.au]

COD4- modern warfare... the Spectre mission is just like shooting ducks ina barrel.. I could do it for hours.

 

[Mystic Beef]

Castle Crashers
Gears or war 2
Cod4
HAWX- i got it despite several bad reviews i saw and it was totally worth it
Left 4 Dead
Fallout 3
Mass Effect

i wouldn't bother with Cod 5 really modern warfare beats it hands down

 

[Eipok Kruden]

Everyone else has listed just about everything by now, so I'll say Halo 3. It is a must have if you're getting a 360. Get the legendary and mythic map packs as well.

 

[theCMNDER]

Infinite Undiscovery and Star Ocean 4, they're the only reasons I'm considering getting an Xbox360 anyway.

 

[thisguyfromthere]

Battlefield: Bad Company.

I want that game so badly. Honestly, the only game I really have for you is Castle Crashers. It's demented, but in a fun way. And Saint's Row 2. It's GTA before GTA IV, so I don't even miss Niko Bellic. Your unnamed gangster is more fun than Niko will ever be.

 

[Spektre41]

If you have even a sliver of love for immersive combat, engrossing storylines, and high octane nightmare fuel, then you have to buy Condemned: Criminal Origins. No high quality 360 library is complete without it. One of my personal favorites.

 

[DoctorNick]

To me, the games:

Assassin's Creed
Condemned: Criminal Origins
Dead Rising
Gears of War [http://www.youtube.com/watch?v=dtGwJo4vadE]
Ghost Recon Advanced Warfighter 1 and 2
Lost Planet
Mass Effect
Orange Box
Time Shift

Are all good places to start because not only are they all either good to decent games, they've been out long enough or didn't sell well enough to be to the point of only costing about $20 at the local Sprawl Mart.

Cheap + Fun = Win

Edit and PS:

If you're willing to spend a bit more cash, then I'll also tack on:

Bioshock
Dead Space
Elder Scrolls IV: Oblivion
Fallout 3

Edit again, I forgot that you had a few games you said you were going to get already. Removed from lists.

 

[sorry user name taken.]

saints row 2 for the lolz

 

[SquirrelPants]

EDIT: Can't believe I forgot Dead Rising. I played it at my friends house. AMAZING GAME!!

It gets really old really fast, trust me.
I'd recommend Bioshock, great game and story. Then there's Oblivion and Fallout 3...The Orange Box, in case it hasn't been said enough times yet. =P