I personally don’t mind which ending a story has, but I like when it fits the story. For example, I really like sad endings because it sticks with you way more than happy endings, but a comedy getting a sad ending out of nowhere wouldn’t work at all. On the other hand, a story that’s been really sad since the first episode would not really benefit from having a super happy ending; it would clash too much. In this case, a bittersweet end could be really nice!
As for the option to choose your own ending, I like it, but you still need to make sure that all endings fit the story, the plot and the characters. If your MC is sad or feeling down most of/all the time for whatever reason, it wouldn’t be realistic to make them all of a sudden a bubbly and joyful person just because they got the good ending.