My favorite is Mario Party 7. It has fun boards and it has great minigames. A usual but phenomenal mario party.
My 2nd favorite is Mario Party 5. It improved what the tragedy mario party 4 did and it improved the looks and the boards, heck even the minigames improved. As well better story but personally doesn't Mario Party 5's story ripped of Sonic Shuffle a bit.
My 3rd favorite is Mario Party 6. It has creative minigames and it improved the flaws of Mario Party 5 and introduces the microphone.
Least favorite is the 4th. It is Mario Party 3 on a hangover. There was only 3 out of the 7 boards there were. Most of the minigames are full of flaws and it has the worst board in my opinion. Goomba's Greedy Gala which is so bad. Generic, annoying, rage making, and most of all luck. This mario party is mediocre.