Ooh, I would love to be a video games character! Well, not at the expense of my current real existence, but alongside that, you know? When I think about a theme song, I have trouble thinking of something for myself/my character personally, and instead think of it as like, the title theme of the game. It'd be something heroic and inspiring, but also light and energetic.
I've been really getting into the music of Malmen lately, so I feel this song fits that vibe perfectly!
https://www.youtube.com/watch?v=wpQKLMg-AJk

As for a fight song, I kind of imagined this as me being on the "other side" of an RPG battle, compared to the player's viewpoint. Since I'm a hero, if you're fighting me that means you've either been a villainous person and I had to leave the party to stop you (a la Sans in Undertale), or I've tragically fallen and there's no saving me so you have to put me down before I cause anybody harm. So, to embody that "bittersweet struggle" sort of vibe, I went with this song.
https://www.youtube.com/watch?v=zuQHHlbzX_c

Oh, and as a bonus, here's a Credits theme for this hypothetical video game. Thank you for the ask, this was fun to answer! :]
https://www.youtube.com/watch?v=fRczf-u2g7I