If you've not played a 3D GTA game I'd recommend you start here. I know GTA III was great, and many people claim it to be better, but for me GTA:VC was, and still is, one of the best games ever to exist. It's dated, yes, but even to today's standard of game it offers things that many haven't since. There are referrences to classic films throughout, and every sign is funny. San Andreas was bigger, yes, but with that space came... space, empty space. In Vice City around every corner was another little joke, or referrence. Every mission made sense in a weird and psychotic sort of way, and you really felt like Tony Montana (something that the Scarface game released after this failed to provide).

I recommend the original Grand Theft Auto because I fear many haven't played it, or even more worryingly may believe GTA III to be the first actual installment. GTA was one of the first games I played on PC and while it lacks the 3D graphics of today's era it is still tons of fun. The modern iterations of the GTA franchise focus too heavily on story and never on an arcade pick-up-and-play style game. GTA was just that. It's fun, pure and simple.

Shocked that I've not yet recommended Portal 2. It's great. It's Portal with an actual story. Granted at times it seems the devs opted to make things too simple in the single player campaign by painting arrows around the place, or making only one small patch of white portal-able wall shine against dull dark surroundings; but with the co-op addition (local splitscreen possible with a few tricks here and there) it's just brilliant!