I liked Fantastic Dizzy the best. I still haven't completed it yet, but I get closer each time I play it. It's a pretty big game isn't it? And that minecart sub-game... love it!
I think Treasure Island Dizzy is dreadful to be honest. One life? What's that all about? It's also incredibly illogical and annoying. Definitely the worst Dizzy game, I'd say.