I agree with the couch co-op. Online multilpayer has become so common that most game developers don't even integrate this co-op mode anymore. Beat'em ups like DBZ or also racing games were games which I particularly loved playing with friends and it never got boring. I also agree with the "more challenging". I used to play Pokemon quite a lot, but over the years they leveled down the in-game opponents to "make it easier for young players". But when I was young the challenging level of opponents was exactly what I loved.
RE: Here are 3 Advantages Of Older Video Games Over New Ones