Usually I go for original controllers and had bad luck with 3rd party controllers for any console.
However, you can't go wrong with gamepad converters to play Virtual Console games using the source systems controllers, can you? Raphnet offers a lot of converters, plus he provides technical specs about his devices that other sellers and manufacturers don't (latency, button config settings, firmware upgrades, etc.):
http://www.raphnet-tech.com/He's even got a PCB for making your own PCE/TG-16 to USB adaptor.
I've got a pair of Hori Pads from a time where they still were like $40 each.
Be aware that the 4 shoulder buttons are awkwardly placed and rather short. People with medium-to-large sized hands like me have trouble hitting them on the right "clicky" spot instead of the button's pivot. And since there are 4 buttons (L, Z - Z, R), often times you'll accidentally hit the wrong one when playing GoldenEye 007 and trying to manually aim and fire. The shoulder button pairs aren't sufficiently spaced apart and don't feel very different, unlike the DualShock or Xbox 360 Controller.
Also, some games that depend on the rather unusual control scheme of having the left hand on the left prong and the right hand on the center prong of the original N64 controller just don't work with the Hori.
Other than the shoulder buttons, the controller is fine. I'd give it a B+ with room for improvement. The best N64 controller so far is the original one, amped up with Micro's analog stick PCB/Potientometer mod + a GC style Chinese aftermarket joystick (ditch the shitty Chinese PCB and potentiometer for Micro's one).
http://nfggames.com/forum2/index.php?topic=5803.0I've got 4 of these kits, and man, they're awesome. It's like blowing new life into the old crusty N64.