It might be a problem with your cable, are you plugging the RCA cable directly into the TV or are you using a SCART adaptor? I found that my SCART adaptor didn't work so I just plugged it in directly.
Alternately it could be just that you need to give the cartridge a good clean with an earbud...
I'd add Super Metroid and Megaman X onto that list. A bit disappointed I missed out because they'll now go for extortionate prices, and I do love some of the old consoles. I still have my N64 plugged into my TV and play it far more than my Xbox