Super Mario Sunshine. I loved the levels and all.

My 2nd would top Mario and Luigi Partners In Time - Gotta love those Alien things.

I agree with you.
Super Mario Sunshine is one of my favourite Mario games, actually.

Also, the title has been corrected.

Yeah, Super Mario Sunshine. Sure it wasn't as OMGAWESOME as Super Mario 64 but it was still a good game. I like the people who say there wasn't any challenge in it. They obviously didn't have to track down every last blue coin.

I outright loved Sunshine myself. Mario and Luigi 2 was also good, but it could have used some work (the Plot progression wasn't very clear). I'm not sure how under-rated this would be considered, or if it is even technically a Mario game, but I really enjoyed Game and Watch Gallery 4 for the GBA. It was one of my first ever video games (the other being Super Mario Advanced), and I still enjoy it today (although the save battery has run dry or was corrupted, so now my high scores are all "9999", and everything else that I hadn't unlocked is unlocked).

Super Mario Advanced

Mario DDR. I had fun with it, and Waluigi was the main villain.

I kinda liked the first Mario & Luigi game. Sunshine left some gruesome goosebumps on me. Aqua- and thelassophobia bite, especially at that damn harbor. DD:

Super Mario Galaxy, because I'm a recent Mario gamer.

Super Mario Galaxy is IGN's number one best Wii game. I don't think it's underrated.
I also choose Super Mario Sunshine. It has a different feel from the other Mario games, and it's one that I welcome. Even after having played through the game multiple times, I can still pick it up and play it again, and even distract myself by diving off of the Shine Gate over and over. :3 It's one of my favorite Mario games and maybe it even surpasses Super Mario Galaxy. Galaxy is a great game, but it just doesn't have the feel that Sunshine has. I can't quite explain it, but I can get more absorbed by Sunshine than Galaxy, though as far as story goes Galaxy is the winner.

I liked Super Mario Sunshine.
I thought the "extra" levels where they played that music was annoying.

But Yoshi was kinda disturbing.....

Luigi's Mansion, although short, was very intricate. I wish i had a mansion like that, although it would be a bit scary at night...

Sunshine. I would actually take that over the OMGBBQ3DMARIO version. I loved the island setting.

Just like so many people here, Super Mario Sunshine. I never understood why people thought it was so bad, as it was really fun to just mess around in, and sure the story wasn't great, but who says it has to be? In fact, I may be the only one on this site who thinks this, but I didn't much care for Super Mario Galaxy at all. I just stopped playing it, despite the fact that I didn't get too far, and I don't know why. It just didn't seem to have the feel that made me want to play it. I wish I did want to play it, because people are always raving about how fantastic it is. Curious.

Sunshine

Super Mario Sunshine was an awesome game

SMS is the most overrated underrated Mario game ever.

I really liked the advance remakes, even though the sound was limited and the screen was smaller, the gameplay was just as fun as the original games, and in a car.

Definately Sunshine. SMS was my first 3D mario game, and I got the same reaction to it as most people had to SM64. It even gave birth to BOWSER JUNIOR. oh, and Toadsworth.

sunshine, only reason why its underrated is because of a talking machine, they could have kept the machine and lose the talking machine part.

other than that it is a great game, full of challenges i quite enjoyed it.