If that's all you haved played, that's less than a quarter of the NA releases. I don't know if it would be fair to use the word "most" in that context.
That being said, while there are some games that are typically considered disappointing in there (like Aztec Adventure, Galaxy Force, Pro Wrestling, and Lost Stars), there are also highly praised ones (like Penguin Land and Kenseiden) so I don't know how much you would like the rest of the library.
If you don't really like hard games, that narrows down 1980s gaming a lot, especially the shooter genre. The SMS has a lot of good ones in that area. R-Type/Kenseiden-level difficulty was pretty much the norm back then for console games (Western computer games tended to be even more difficult).
I think SMS gun games tend to hold up better than anything else in that genre from the classic eras but if you don't like those kind of games, I guess that's not going to be a plus.
It might not be the system for you but I would recommend checking out some of the not-as-difficult '90s releases on emulator like the Mickey, Asterix and Sonic games, Alex Kidd in Shinobi World (it's more like Shinobi than Alex Kidd), Bubble Bobble, Ninja Gaiden, etc.. That's always the quickest (and cheapest way) to see if you want to invest money into old systems.
Anyway, I think it's cool that you like some games on the system. Most gamers your age probably wouldn't even touch it.

And I think there's a lot the SMS has to offer for Genesis/Mega Drive fans given the overlap of development and franchises from Sega back when they were a top tier game maker.