I gotta admit that even for me initially I did not like Jinbe's appearance. I remember a ton of vocal disappointment. When we had guys like Arlong, Kurobi, the silhouette of Tiger or even Macro I think everyone had a very different imagination of what he would look like, especially when you combine it with the fact that his fish species is one of the grandest of them all.
The wait to actually see what he looks like was epic and I suppose that build up was going to set expectations too high. I figure if he ended up looking like Hack or more in line with Arlong the reception would have been better.
Personally I like Jinbe as how he is.It wouldn't make sense if Jinbei was not huge looking,would it? As a Fishman based on a Whale Shark he had to look big and grand.Fishman are generally potrayed to be superior to humans in general.If Jinbei was just tall and wasn't big horizontally he might as well be just another Fishman.I mean,Arlong and Hack are generally taller than your average humans like Usopp and Sabo.They have their fish species characteristics with their nose and that beard like thing so that criteria is checked.And as they are physically superior to humans they might just be tall as well,so that's checked.Their looks make sense but if Jinbe wasn't "fat" his looks wouldn't make sense as a Whale Shark Fishman.I would rather Oda make sensible looks for characters especially Fishman than just try to appeal to some readers like he does with almost every female having the same body type.I like big cuddly people so I like Jinbei's looks.Matter of taste I guess XD