Two games that are really fun, last long, have replayability, online multiplayer and regular updates.
Circuit_strike.one for me as well!! I really don't need a second game after this!! But my second pick would be real racing. It's just so damn impressive.
Bobble Surfer and X2 Football Both have open ended gameplay, so you never can "complete" them, the fun just goes on and on
Definately Puzzle Maniak and ... Second one would be a toughie, would have to be some sort of action game, maybe Isotope (I'd eventually reach a decent max score) Eliss (maybe then I could finish it!) or Flight Control (which is my current 'short time' killer...)
Damn.......... I'd have to say Star Defense and Star Hogs, and when A.D.D. comes out I'd replace Star Defense with that.
Quantum Collapse because I absolutely love RTS games. and the skirmish mode would add a lot of replayability, along with the multiplayer that is coming. I would also choose GL Golf Deluxe. There are so many courses you could play this game for a loooooong time.