4th Gen What did you dislike about it?

I don't dislike sinnoh. I dislike the shape of it and the layout.
At first it's all complex and you think it'll take you yoinks to go through it all.
Then you find out, at least 3 routes you don't even get forced to go to by road blocks or nothing.
A fifth of the place isn't even connected to the region and isn't accessable till ever the league and pokedex? That's just a pain as well.

One of the bad things is in Platinum, you never get to battle Charon. I wanted to battle him, but Nintendo decided to not make him battleable. That was a disappointment for me. And the slow surfing speeds in Diamond and Pearl were atrocious. In HG/SS (This is before I played Crystal, but after I played both Blue and Firered) I was quite disappointed because Pokemon Tower in Lavender Town was a lot smaller than in Firered and Blue. But that was it.

For me replay value. I used to play over 15 replays of my old Gold... now I can't bring myself to finish my third one in SS. This may not be the case in Pt, but I have so many pokemon in it I never restarted.
Sinnoh, was awesome. I loved it. the pokemon were in some places horrible, but it had several good ones (Lucario?), and some evolutions of old ones were good (Gallade, Electivire). I thought IV gen was exceptionally good. Game freak pulled off the transition to DS quite well.

I disliked how you were forced to get the Icicle badge in D/P. You trudge through a blizzard to reach Lake Acuity for the sake of the plot... And two Galactic Grunts block the entrance to the lake. You can't fight your way through them, despite that being the entire reason you came. You have to get the Icicle Badge because you're waiting for the evil plan you came to stop to finish.

The D/P/Pt games were pretty good i played it for hours on end but in the HG/SS near the end after you get all 16 badges you just get bored because there's nothing really to do.

What i didn't like mainly was something in HG/SS.
HG/SS Didn't have the Vs.Seeker which is horrible for the fact that Pokémon like Dragonite and Arcanine take forever to train.
I didn't like the Legends in D/P/Pt but that's all i can say.
4th Gen was one of the best with very little flaws i say.