The Genesis did 320×448 interlaced and wasn't capable of progressive scan.
I'm looking at wiki. Are you looking somewhere else?
Besides, neither really means much in terms of sprite size and quantity, and there are very few SNES games that make use of the progressive scan option (IIRC).
I agree with you (and the others) about shmups. I'd way prefer slowdown-less gameplay over color layering, mode 7 effects, etc. Slowdown is like the worst thing possible in a shooter. Just ruins your rhythm. I never played sports games, but I imagine the same would hold true for most folks.
"Better" or more sophisticated graphics are great, but history has proven that it's not the the most important feature with regards to selling units. The PS2 was technically the "weakest" console of the 6th generation (save for the poor DC), but it outsold the competition by a massive margin. It's all about the games, and in the 16-bit era, exclusive titles were plentiful. You had to seriously consider what games you liked, or thought you would like before buying a console. And back then, try before you buy wasn't nearly as easy as it is today.
I recall many friends literally selling their current 16-bit console to buy the other when a certain game dropped. I had at least a few friends sell their SNES when Sonic came out, and other that did the inverse for Street Fighter. I was really fortunate in that I had a SNES and my younger sister had a Genesis (for all the sweet Disney games).
Which brings me back to the OP's Q. Disney games were kick-ass on the Genesis. Some I liked slightly better on the SNES, like Aladdin, but if I had to pick one console for that type of game, it would be the Genesis hands down. Quackshot and Castle of Illusion were just plain awesome.