At my local gamestop, you can get both Mass Effects for 16 euro. Which couldn't be much more than 20 dollars.
If you're still looking for suggestions after what you bought, may I highly, highly recommend Forza Motorsport 3. Or pick up some microsoft points and get Toy Soldiers off of XBLA, good ****. Also, if you have real, living, breathing friends who are able to physically be present in your house, buy Castle Crashers. If you're (legally) able to consume alcohol whilst playing Castle Crashers combine the two for an epic combo attack.