I feel like there's two kinds of feel good movies IMO. Some are just people overcoming big obstacles by the end, and others are just light-hearted fun the entire movie.
For this, I'll list the latter. Some of these were my mom's favorites and I like them as well after watching them with her.
- Ocean's 11 series (both the original and remake movies)
- Music and Lyrics
- The Intern (with Robert Deniro and Anne Hathaway, in case there's other movies with a similar title)
- Office Space
I vaguely remember "Must Love Dogs" being light-hearted fun but been too long since I watched it.