The only reason I bought a Gamecube, and thus got back to console gaming some years ago was that I ended up with a bad case of Super Smash Bros. Melee addiction after a few hours of constant exposure one night. I guess you could call it a system seller for me.
The same could be said for Halo1&2 for the Xbox, since the way I got mine was by borrowing them all from a friend who didn't do much with them, and finally buying the whole lot for 50€, but that was more about collecting than anything else.