No game has been a system seller for me since PS1/N64
I got a PS1 for Spyro and an N64 for Super Mario 64 (ironically, I never got SM64, but got the N64 because I thought the game was awesome)
I wanted a Dreamcast just because it was the new thing, but I didn't get it until like 2001 when it got liquidated and was $50 (which I bought in $1s from saving allowance).
I got a PS2 because the PS1 was just so awesome, and all my friends had PS2
I got a PS3 because this is the first generation where I'm in total control of my game purchases and research. With the PS3, I strongly followed the "just wait" motif, and bought it at $400 knowing that all the great Sony IPs would come to it, along with 3rd party games like GTA4 and MGS4
I got a 360 because it just so dominating in the US, and all my friends had one and were playing CoD4 and Halo, so I just bought one. It was also, however, an impulse buy because someone I worked for had sent me a check for $200 for doing little work for him (he overpaid, by ALOT), so along with some game trades, the 360 cost me, out of my own personal pocket, like $15
