Anyone who dislikes any of the Rocky films (including 5) isn't worth their weight in salt. They're all fantastic for their own reasons:
Rocky - A truly great film, easily the best underdog tale in cinema history. Gripping drama and an adrenalin pumping finish.
Rocky II - Essentially The Godfather Part II of the Rocky franchise, arguably as good as the first. Rocky in the space of a couple of hours makes himself into an underdog again and then gets the ultimate reward leaving any viewer satisfied.
Rocky III - This is where my main issue with the thread starts, you claim that Rocky IV was unrealistic and that it should have ended with III, however what the hell was realistic about Rocky III? This is one of (if not) my least favourite of the series but I'd still watch it any time. It's all about the eye of the tiger and Clubber Lang.
Rocky IV - Easily one of the most entertaining Rocky films out there and for completely different reasons to the first. This film is all about the action; the montage king. 2 quality training montages and the other one that reminisces over previous endeavours. It all gets you pumped up for the big fight against the evil, steroid using, comic book villain. Mix all this with the series' best soundtrack and you've got yourself a delicious Rocky pudding. If you're a hater, you're watching it for the wrong reasons.
Rocky V - Time to get controversial. I see this film as an after dinner mint. You've just had a satisfying meal but there's always room for that wafur theen mint. It compliments the other Rocky films well. Rocky get's taken back to his roots and you get the pleasure of seeing him remember it. This film would probably be better if it wasn't about fighting at all, with Tommy Gunn taking a long walk off a short pier. But a few choice performances and touching moments more than make up for it's flaws. The credits alone make the film worth watching (and not because it's the end of the film)... Pictures from films past, with "The measure of a man" playing... brilliant.
Rocky Balboa - Simply a fantastic addition... Probably the most true to the original. Get's you rooting for Rocky. Questionable editing, with a couple of choice scenes missing the final cut. But a great film... It's almost too realistic though. Mason Dixon is just too real.