To be fair I've only watched from BB1 to BB10.
Overrated: BB9 and BB7 (like it a lot but it did lose it's way mid way through, doesn't deserve to be anywhere near the top of BB's list)
Underrated BB4 (go ahead and shoot me
, but I think it's far better then many give it credit for, no it's not a classic but it's nowhere near the worse imo)
BB10 (I thought it's first weeks were top notch, although it did badly lose it's way in it's last few weeks and I didn't like Sophie winning it she was undeserving and that every guy was fawning over Noirin and the show was kneeling to her demands. Also it has one of my most hated guests in Bea, she made for a great villain. But it's got some of BB's greatest moments and is deserving to be held up alongside peak BB for me)