I also have a potato PC with 4gb ram and i3 processor and these are some games which run finely in my PC:
- Batman Arkham Asylum ,City (action adventure game as batman)
- Call of duty modern warfare 1, 2, Black ops (linear FPS game)
- Elder scrolls V : skyrim (huge open world rpg)
- Super Meat Boy (2d platformer)
- Portal 1, 2 (puzzle)
- NFS most wanted 1,2 (Racing)
- Far Cry 2,3 (FPS with open world)
- Euro truck simulator 2 (driving)
- Rocket League (football with cars. its really fun)
- Inside (puzzle)
- Half life 2 (great FPS but graphics is little dated)
- Assassin’s creed 2, Black flag(stealth, action)
- GTA san andreas (you’ve probably heard of it)
- Left 4 Dead (online multiplayer. Zombies)
- borderlands 1,2 (FPS, RPG)
- Minecraft (no limits on imagination. don’t play this one 4 graphics)
- Dishonored (great stealth game)
- Prototype 1,2 (action)