Atari 2600 Jr, NES, SNES, PS2, GBA SP. That's it. Well, I also have a TI-99/4a, which is more of a computer, but it uses cartridges.
I think the PS2 & GBA are going to be the last consoles I buy. I just can't get into the newer games. I liked GTA3, and to a lesser extent Vice City, and the girlfriend likes DDR2 Max, but other than that the PS2 just collects dust. I haven't touched the GBA since January, and would love to sell it, but the girlfriend wants me to keep it around for trips and such.