These are lots of fun!
There are many games that I loved and would enjoy playing for the first time, but I’m going to pick Mario and Luigi Superstar Saga. My reason being that I spent the vast majority of the game waiting for it to morph into a spiritual successor of Super Mario RPG back when I first played it, rather than giving it a chance to stand on its own as a unique and hilarious game. My preconceived idea of what I hoped the game would be really hurt my initial enjoyment of it.
For a runner up, I’ll mention Kirby’s Dream Land 3. In the days of Blockbuster rentals, I’d rented Kirby Super Star first, so it took me a while to get used to the more traditional Kirby powerup system where copied abilities only do one type of action each.
I tried the iOS beta until it expired. Didn’t know it ever made it to the app store.