Am I like the only person who posted here that owns all three?
Anyway, my favorite would have to be the PS1. The Genesis does have good games, but I feel that the Playstation has more great games, such as Spyro and Final Fantasy games. The Dreamcast, even though I love it to death, doesn't have that many classic games aside from Sega games, Soul Calibur, and Marvel vs. Capcom.