Made a couple of updates to the list. Yo, Bro is actually alternating, not simultaneous, so that was moved. Also, added bolding for a few soccer games I missed (Formation Soccer '95 and J.League Tremendous Soccer '94). Also Shibubinman 1 is of course also co-op. Break In also allows for any mix of humans and computers (it's a pool game), so I bolded that as well. Bonanza Bros. is another co-op game I'd missed; it's bolded now. Same for Forgotten Worlds.
But how are some games, like The David Cup Tennis, 5 player co-op?
It's four player - two humans vs. two humans (or cpu).
Yeah. That bolding might not be entirely accurate though for the sports games, because I didn't test everything to find if they do all have 2 human vs 2 CPU modes, but any team sports game that supports more than two players is definitely going to be co-op in some fashion, so I bolded all of those. I didn't bold golf or olympic sports titles, because I assume that those are individual games. For the other ones (baseball, soccer, football), the question is about whether they allow 2+ humans vs. computers, or if the 3-5 player modes are just humans versus humans, and whether you consider that co-op or not. Also I didn't bold any wrestling games. I assume that they're all free-for-all games, but don't know if there's a team mode somewhere or something.