Kakashi is NOT one of the weakest ninja's in the Narutoverse regardless of what you see. He is not my favorite character, but I still think he is an amazing shinobi. I don't think he is on the level Minato or Itachi, but he's very close.
Kakashi has beaten almost all of his enemies and is renouned in the ninja world as feared memeber of konoha. Of course not as renowned as Minato or Itachi, but still its enough to make people aware of his abilities and that fighting him is not going to be as easy as some people think.
He is skilled with most elemental jutsu, kicks ass with his sharingan, smarter then shikamaru, better at taijutsu then lee. He always see's past a ninja's abilities, even if he can't beat them.
His major downfall is that he can't maintain sharingan for too long or else is servilely wears him out, and bed riddens him for a week. His other major downfall is that he is a low chakra ninja, which is a big one, and why he must always be battle conscience and can't let the fight go on for too long.
The reason why poeple think he's weak, is most likely because he did very well against, or beat their favorite character.