I think it depends on which era of Genesis software you're talking about.

Very early Genesis games do look and sound quite primitive. Games from 1989, 1990 and 1991 especially. Genesis games from 93, 94 and 95 aged pretty well all things considered. The audio on the Genesis just can't compete with the SNES, so it's an unfair comparison. As well as Yuzo and company did with that audio chip, all the scratchy, AM sounding audio, didn't do it any favors. Also, Genesis could only put 64 colors on the screen simultaneously. So, it's really hard for it to compete from a color standpoint. Having said that, there are still some very colorful games on the Genesis, especially if you see them on a RGB monitor.