Silly question really.. ;-)
If its a great game, it's worth paying for.
Doesn't matter if it's for a console or a PC or a phone or a retro system.
I buy new games for my Vectrex and Atari 7800, so for the Amiga, sure..
Of course, price will make a difference.
There are great games available for the Vectrex that I won't buy just because they cost too much for me. Now, I'm not saying they aren't worth it. They are incredible looking. But I don't pay that much for games on any system.
However, if a game is fun, good quality and in my price range, it'd be silly to say "well, I know I'd enjoy it, but since it's on the Amiga, I'm not buying..." ;-)