Maybe it's just nostalgia clouding my memory of this one (it was my very first Mario Party game after all) but I think Island Tour is pretty underrated all things considered. The minigames were a ton of fun and used the system's capabilities in a bunch of cool ways, the boards were really creative concept-wise (execution-wise....eh, not so much) and Bowser Tower was a really good side-mode that kept me coming back over and over again.

Overall, Mario Party Island Tour is pretty much the video game equivalent of a drive-thru meal: hollow when consumed anywhere but on-the-go, but a nice time within that context.