It's easy for me, I decide console based on what games I tend to play:
Sony PSX = RE Directors Cut, Silent Hill, RE 2, RE 3, Medal of Honor, Metal Gear Solid, Final Fantasy, Chrono Cross, Crash Bandicoot Racer
Sega Dreamcast = RE Code Veronica
PS 2 = RE 4, Silent Hill, 2, 3 ,4, God of War, Metal Gear Solid 2, Medal of Honor 2, a few random titles
Nintendo Gamecube = RE (remake), Rogue Squadron
So as you can see, I've got a bias towards Sony.
I actually only bought the Gamecube with the understanding that it would release the next 6 RE games (not realizing that they basically remade the first, PORTED parts 2 & 3 directly, made a shitty RE 0, and then released RE 4 which was better on the PS2 anyway).
So yeah, I'll stick with Sony. I just prefer "mature" titles. If I want Super Street Fighter Turbo, I'll pull out my SNES.