If you had a good/great PC, which Emulators are in your 'must have' list?

Since the colder weather is setting in, and the production on my cab is slowing (sadly), I'm looking to fill my down time with getting my PC, TV and CP configured, so that I can set it up in the corner for the kids to play with. (For when I start on the other parts of the cab, of course.) My question is this. Which emulators do you presently use, or would you use if you have a good/great PC?

I am pretty comfortable in my collection of MAME games, but I really don't know which other Emulators are a must? I've been reading that going with a Dreamcast would allow you to replicate the arcade experience on a lot of 'higher quality' games, but would a Dreamcast Emulator give similar benefit? If I'm using a TV, and am stuck using 640x480 resolution (or close), will a PS/2 Emulator allow me to play good games on it?

Another concern I have are knowing what other emulators lend themselves to using a joystick and buttons, or if I add a Commodore 64 emulator (my Wife LOVES Jumpman Jr.) do I then need to add "Load" and "Save" buttons to my Admin Panel?

I always planned on having MAME on my cab, but these other emulators confuse me. Probably because I don't even know what games I'll enjoy on them. (I've never been 'the console guy' - I've been playing FPS using keyboard and mouse for the last 15+ years.)

L'il help?