I love the Atari stand alones, still having my Video Pinball hooked up, but I can't get into all the other systems of that era.
The 7800, Colecovision, and Famicom with disk system keep me happy on the early gaming front. I've had a Sega Master System, Odyssey 2, and Intellivision (w/The Intellivoice, ECS, and Keyboard) and just never got the systems.
I still have my C64 and Atari 800XL, but I dropped my TI99. I even had the MBX add on for the TI, but couldn't justify keeping it with only and handful of games and maybe 1 or 2 of those being good.
Someone else mentioned loving the Genesis over the SNES and i'm in that boat as well. Except for Super Metroid, the SNES' library just never hooked me and that sound chip really bugged me. The Genesis may have been noisy, but that Yamaha FM sound just sounds so cool.
The N64 was just too ugly graphically for me to enjoy getting into it. I just parted with my PS1 and Saturn so I'm pretty much done with collecting for that time.
Of the modern stuff, I have a PS3, PSP, Wii, Wii U, and 3DS. I have them mostly since I can build up their Digital only and Virtual Consoles without packing my shelves with more stuff.