Meh, I guess you're right, I'll try. For every season.

Season 1:
Underrated: Mermaid Man and Barnacle Boy. Only 2 or 3 more episodes in the Best Episode Ever Contest to go until I start voting for this episode. A great early episode with tons of funny parts, I don't get how it's the last pre-movie episode left, and generally treated poorly.
Overrated: Scaredy Pants. I'm sorry, but I found this episode boring. Nothing I truly dislike about it, just never really appealed to me.

Season 2:
Underrated: Band Geeks. YES I SAID IT. I know I made a thread about it very recently where some people weren't too happy with me, but I don't cared. A beyond amazing episode, my all-time favorite. I DON'T just like it for the song. It has some many other great parts, Squidward winning, and tons of awesome humor, like "do instruments of torture count?" and SpongeBob's "eager" face. An all-time great that EVERYONE calls overrated.
Overrated: Just One Bite. It was a fight between it and it's partner The Bully, but at the end this one won. I don't hate it, but I found very few parts funny. The Squidward abuse leaned more towards unfair abuse than humor, and it got kinda bland at moments. It did have some OK parts though, like the deleted scene.

Season 3:
Underrated: The Sponge Who Could Fly. Perhaps the only underrated Season 3 episode, and boy how much is it underrated. It had tons of funny parts, an awesome song, actually half-decent Patchy, all good stuff. In my Top 10 for S3, which is an accomplishment. Overrated: Club SpongeBob. Where you honestly expecting me to say something else?

Season 4:
Underrated: Dunces and Dragons. Here is a fact you will not believe. This is my 4th favorite episode, after Band Geeks, Chocolate With Nuts and Christmas Who?. It had tons of funny parts, an awesome plot, and most importantly....Squidly! I seriously cannot get enough of this medieval masterpiece.
Overrated: Wigstruck. A boring episode that gets decent reception. Not much else to say, just...boring.

Season 5:
Underrated: To Love a Patty. I liked it. It had some decent jokes, and a great song. They actually made something out of the worst plot in SpongeBob history.
Overrated: Sing a Song of Patrick. I found it little more than typical Season 5, mindless and boring. I didn't find the song funny, just stupid and random.

Season 6:
Underrated: Penny Foolish. Here's a news flash: MR. KRABS IS SUPPOSED TO BE CHEAP. Yes, he was stupid in this episode. But in a FUNNY way. Do you honestly think they were meaning to make spending hundreds of thousands of dollars to get a penny realistic? Um...no.
Overrated: Boating Buddies. A totally cruel Squidward episode. One of the few episode where I found the Squidward abuse disgusting, and totally unfunny.

Season 7:
Underrated: Shell Shocked. Out of all the lesser well-received Season 7 episodes, this one was the best. I found it pretty funny, and a reference to a previous episode (Shell of a Man) is always kinda cool.
Overrated: None. I have not disliked any well-received episode so far in this season.