The more obvious must-play staples are in there (Yoshi's Island, Super Mario Bros. 3, Link to the Past, Super Mario World, and Super Metroid are all legitimately great, with a handful being genuinely among the best all time), and it's absolutely worth paying the subscription fee just to experience them if you haven't already and otherwise wouldn't elsewhere. In my opinion, the best way to experience them is by buying a SNES Classic (if you can find one), hacking it to add all the emulated games it's missing, and having the authentic experience, controllers and all, but this way may be more convenient/feasible.
It's more underwhelming for a lot of people just due to the fact that they started off by releasing an inferior collection of the existing SNES Classic offerings (which shouldn't require much effort at all on their part), and they're just slowly doling out obscure games that generally aren't worth playing, despite the fact that there exists a treasure trove of significantly better games available for that console that they're taking their sweet time with for no reason other than because they can milk it over a longer period of time.
Considering how limited the library is right now, if I were you, I would just subscribe, beat those games (maybe try a handful of others like the Super Mario Bros 1, 2, F-Zero, and Super Mario Kart), and then cancel.
I mean, Super Metroid alone is better than most $60 games today.