On snes I've always used a ASCII pad, I got one bitd and never looked back,

For nes I got rad turbo pads as a kid and o
Loved them until a few years back,

The rounded edges and slightly larger size were as much of a benefit as the turbo features.
I recentishly discovered these pads and they are definitely my favorite for nes, nice weight and adult proportions.

For sega I used stock on all systems (master syste I ended up using Genesis pad on once it was an option.)
Nes snes and n64 are the only systems I've switched to third party on controllers for, except for the aforementioned Logitech ps2 wireless controllers which are fantastic.