The games I own are (by order of their release) and which platform I play them on:
• Grand Theft Auto - Rockstar Classics Free Edition (PC)
• Grand Theft Auto 2 - Rockstar Classics Free Edition (PC)
• Grand Theft Auto III (PS2)
• Grand Theft Auto: Vice City (PS2)
Grand Theft Auto: San Andreas (PS2 & PC - I play on PS2 to do missions and play alone, on PC because I have SA-MP and I like to play it online)
• Grand Theft Auto: Liberty City Stories (PS2)
I have some friends of play GTA 4 and seen lots of videos and screenshots about it. But I still think GTA: SA (my fav. GTA) pwns it. Old school (almost) always pwn.
So please, vote!