While looking for stuff on GB Studio I found this other tool called NESmaker.
It's not open-source or free (USD$36 iirc), nor as easy to use, but still seems pretty cool.
Here's a page of demos you can play in your browser:
Witch City is pretty!
Hi! I hope Game Making Social is a cosy, friendly place to talk and share stuff about amateur videogame making and everything surrounding that. It's kinda an offshoot of Game Making Tools, which is a wiki(+) for a similar audience.