Pang on the Amiga is more slick and plays a lot better than the arcade version. Amiga Rainbow Islands is also better than the arcade imho...
On the C64 I always liked Gryzor - different levels than the Contra arcade and a much better difficulty level. C64 Ghosts'n'Goblins is also more playable than the arcade version. The Amiga version of Ghosts'n'Goblins is extremely faithful to the arcade too - but that makes it too hard and it has annoying slowdowns.