Fantasyland will most certainly be the best once it's expansion is over. As for now it's really hard to beat Frontierland for me. Country Bears, Splash, Thunder, Sawyer, etc. I guess the only thing you can say is that Adventureland has probably the best ride in the park with Pirates. There are few rides (none I have ever been on other than Haunted Mansion) that give you the feeling that ride does.
To the poster who wants Jungle Cruise "ripped out" all I can say is, huh? It's still a great experience. I'll admit a ton of things could go into Jungle Cruise in its replacement but if they want to add anything they should add stuff rather than replace it.
Tiki Birds and Aladdin don't add a whole lot of value to the land but they exist, and while people complain about Aladdin being there (it really fits more in Fantasyland) does it really make the land worse?
Swiss is one of my favourite attractions too. Simple yes, but you don't realize how awfully high you get. There are some great opportunities for pictures up there too. Besides, it's a treehouse that you climb, how cool is that? I've always loved it.
At the end of the day I can't make a case for Adventureland to be the best. Most people would probably pick Frontierland, or at least I would.