SM is a good choice. So is WOZ if you Can get past the theme.

Get something deep even if it's longer ball times. LOTR, SM, WOZ, DI?

If I only had one pin (and I only have two right now). It would be SMVE. I love the vault package, but original is fine too if you're into that. And if it gets too easy, you can remove the center drain post. Then, you can add lightning flippers to give it even a more difficulty level if need be. The rules really are built for brutal games (risk/reward with multipliers + not too deep in progressing). I've had mine 8 mos and really really like it; but you do seem to play more pinball than I

Oh one other suggestion. FGY! If you like the theme, and don't mind the adult'esk humor around your kid (there's a setting to turn off adult language). But this game is comedy gold + some deep creative Keefer rules. I love it and the theme integration is one of the best. If you go this route, you need to make Stewie pinball harder in the settings and even may swap out the Stewie ball with an even smaller one. I think pinballlife has them?

Of the 3 you've owned, which did you like the most?

I believe he got Guardians of the Gunniea Pigs.....err I mean Galaxy.