Then Morrowind had even better longer quest with an even better magic system but the Game was far uglier than Oblivion without mods of course.
Oblivion richer quests? The only thing that comes to mind when thinking of richer quests in Oblivion was the dark brotherhood. Every other quest line ( factions, mq, single quests ) were nothing more than fetch this and kill that. The main quest of Oblivion was nothing short of horrible writing.
I really like Bethesda and their games, but Oblivion was by far the worst game they ever made. It was nothing more then an empty benchmark showcase husk with a bit of content added to it.
I choose Morrowind's graphics over Oblivion any day. Why? It had style and identity. Oblivion was another generic fantasy action game. I did enjoy it though, but not without mods. I still play Morrowind today, unmodded.
Mind you, I'm stating my opinion here and not attacking you. I simply feel very different about Oblivion.
This is however about Dawnguard and I dare say, it really is worth the money. However, this will always be a matter of taste. Some of the complains really are valid while others are silly. You can't have a game with everything in it. So, no matter how hard Bethesda tries to create an all round game that will appease to every gamer, they will never succeed. Everyone's taste differs, which is why Bethesa is not the only gaming software in the world and the elder scrolls not the only game franchise. Play other games if you don't like it. And if your newly acquired game is not to your taste, you probably should have informed yourself better.