So are there any of those games that you thought had a great and rewarding ending? Also, were there any that were better than you expected?

No particular order...

Mario & Luigi: Bowser's Inside StoryWhen Mario, Luigi, and Bowser all reach level 40, they get gear that really helps in battles. Especially for Bowser, since his makes him have 2 moves per turn. Also in the end Chakron the sage says he is proud of everyone and he does not say he is proud of anything ever. Mario and the others also made a cake for Bowser, since he helped save the Mushroom Kingdom from the Dark Star, so it was nice that they acknowledged that.

Donkey Kong 64When everyone was celebrating after defeating King K. Rool. Also the quirky blooper reel when you get the 101% ending is just... lol.

I'll add more if I can think of some...

MGS Games, with the casting theatre/secret theatre, and having the ability to play again with what you've unlocked (I guess that goes for a lot of other games with NG+ as well). Another thing they do, which I love to see in any game or even movie, is using post credit scenes.

Beyond Good & Evil had en excellent ending, one of my favourites (don't know how to spoiler, so I'll just say you need to play it to see what I mean).

I find the most rewarding thing in videogames is finally beating something really challenging, or having a final boss with an awesome song. For this reason, I have to mention the Armstrong fight in Metal Gear Rising. It took me hours to finally beat him, but because I loved the song, it didn't really feel like a chore.

Adversely, I'd like to say, in my opinion the least rewarding thing for me was collecting all the power cells in Jak and Daxter. My 10 year old self could not comprehend the fact I had spent so long finding them all, for nothing basically.