Isnt miracle world considered the besr ak game with only 1 or 2 other games being good?
Miracle World and Shinobi World are pretty good (the latter is a bit short, though).
The Lost Stars is fun, but it's also quite simplistic and linear. Each level you just run from left to right to the exit, with hardly any verticality in the levels.
I've never played the arcade version, though. That one has co-op play, which might be a nice way to experience the game.
High-Tech Land is supposed to be atrocious. It actually even isn't a 'real' Alex Kidd game. It's based on some Japanese cartoon and was rebranded as an Alex Kidd game in the West.
Gameplay-wise, Enchanted Castle resembles Miracle World the most of all the sequels and spin-offs. I haven't played it much though.
There's also an Alex Kidd BMX game, but I don't know if that one's worth playing.
From all those Alex Kidd games I mentioned, I've played The Lost Stars the most. It was my first Alex Kidd game and the colourful graphics and simple but fun gameplay kept me coming back.