I've got 8 sterns now, and what I like best is probably a little off from most opinions:
1. Stranger Things LE - super popular at my house, great schtick, fast and easy to play. It's my 6 year olds favorite. If you suck at pinball, it's a good one because the shot mechanics are pretty simple
2. Guardians of the Galaxy with the proper sound code
3. Deadpool or AIQ - I dont own either, but I'd add either one
Honorable mention - If you can find a Tron LE, that's #1 by a mile. It's incredible.