Let's look at the Fighter's Guild as an example.
Morrowind has 31 Fighter's Guild quests, Oblivion has 19.
It's not strictly about numbers though, let's delve a little into those quests.
In Morrowind, the first quest is to go to someone's house and kill all the rats. You go upstairs and find every single barrel and cabinet is stuffed to the brim with pillows. It's amusing, but you kill the rats and get your money. Later, completely randomly, you can actually find an unmarked sunken ship full of pillows, with a shipping note saying it is addressed to that one NPC.
In Oblibion, you also get a rat problem quest, for a very similarly named NPC. You go and find out you're actually trying to save the rats, it is an amusing twist, and have to take several steps to find out how and why the rats are being attacked.
Oblivion is amusing, but relies on outside content for the joke to be funny.
As the Oblivion quest line progresses, you just do random quests, eventually with the final person giving you quests regarding the Blackwood Company, who are basically just the Evil Fighter's Guild and you can't join them. Eventually the master of the guild makes you master even though she hates you because... reasons I guess.
In Morrowind, the Fighter's guild quests pit you against the Thieves Guild, a guild you can join. In fact, unless you do thing very specifically, they are mutually exclusive of each other. It's not just random bad guys, each play through can put you on either side of their fight. As the quest line progresses, you find out the guild leaders all have different priorities, and maybe aren't who they seem. In fact, they've been making you do some pretty shady shit. If you trust the right people, you can learn how the guild plans to betray you. Once you reach the leader, you kill the leaders of the Thieves Guild and then he tries to kill you, and you become leader thanks to making allies and killing the old one.