The Vectrex would need to be in that poll to, partly because you simply can't emulate it properly -- you need the real thing to appreciate all that vector-y loveliness.
Personally, I can't go past the SNES. I had (and still have) a super wildcard (backup unit), so played every single game as they came out (0-day releases, how cool)... some great memories. 4-player Bomberman, endless Mario Kart duels, marathon SF2 Turbo tournaments -- heck, it even had a great version of Sensi! And of course, the majesty of Zelda 3 (and Final Fantasy 3, come to think of it). Unbeatable. The best part was, it would also convert & sometimes improve more 'serious' Amiga titles like Sim City, Civilization, Populous 1/2, Mega Lo Mania, etc.
However, I've recently started playing around with PC Engine emulation again, and it's a damn good machine -- some of the arcade-y stuff done on it was pure gaming bliss.