Nope. Oblivion was my introduction to the series.
Ah, then you can't see where I'm coming from as almost all of my complaints would reference Morrowind...but a couple ones you could get, they cut the number of factions you can join in half practically, majorly curtailed your freedom as Oblivion introduced characters you can't kill (in morrowind you could screw up future quests by killing someone important or even break the main story, but the game would tell you if you killed someone crucial to the main plot so you could reload if you so choose) and items you can't drop, switched from an innovative and imaginative world to generic LOTR-type fantasy fare, the scaled leveling system in Oblivion was horrendous by any account (why you could do any quest, or go to any area whenever you felt like in that game, it adjusted it to your level, whereas previously things were more set. I beat the oblivion main quest at lvl 7, in morrowind there were plenty of bandit caves (something else they were lacking in Oblivion...they filled caves all monsters instead of having some filled with bandits with robinson crusoe type hideouts) where you would be murdered in less than a minute if you went in that level), magic is completely broken in oblivion...conjuration especially made everything pitifully easy while other skills like mysticism (used to have enchantment and teleportation spells) and alteration (you used to be able to levitate!) have been made useless as is security/lockpicking since you can get an unbreakable skeleton key at level 10 in oblivion.
All the ruins are made out of grey stones in oblivion, even in the expansion set, how fucking boring is that. Morrowind had your stone medieval shit, steampunk dwarven ruins, daedric ruins which weren't some generic lava-world crap. Each region of morrowind had it's unique architectural style (giant mushrooms conveted into buildings on the rather sparsely populated and xenophobic West, more clayish normal buildings in the richer southeast, oddly shaped things in the desert, stone type buildings in Imperial settlements, wooden fishing villages, a bunch of giant bunkers floating in the water for the cultural/religious capital. The world was full of unique things for you to find if you took the time to go to inaccessible places (more shipwrecks, underwater caves off random ass islands around the coast, etc. etc.).
Then you have stuff like the omniscient quest compas in oblivion that tells you were everything is. Before people gave you directions, like go look for this rock and head southeast...it ended up being more northeast probably but you found all kinds of awesome stuff when wandering around looking. And you couldn't teleport isntantly to any location you had been previously, you had to walk to a town and take a transit system (boat, silt striders, or mages guild teleportation) or huff it...why did they even add mountable animals (boring ass horses) in Oblivion if they let you teleport instantly? Plus the shape of the world was a bowl so you get anywhere pretty quickly (all the mountains are at the borders) it made it feel a lot smaller than the island of Vvardenfell in morrowind which had the endgame area in the center of the map, volcanic and mountainous so walking would be extremely inconvenient, with higher level enemies that could make short work of an unprepared player. Plus, Cyrodil, where Oblivion takes place was described in books found in previous games as having rainforests and being in a tropical climate.
And let's not forget the mainquest, where you are that one dude's glorified manservent just doing what you're told through the whole game and not even getting a final boss battle. Your character was entirely superfluous. In morrowind you had to unite rival political factions (one was a bunch of wealthy merchants with a leader who you could sway to your side by stripping for him, one was an honor bound desert warrior cultural, and the other a bunch of misanthropic wizards who you could simply murder if you so chose), indigenous persons, and in general be an active important part of the plot.
I'm going to stop now, I have about 20 other complaints still on the top of my head, but I haven't gone into much detail about the previous ones. I could go about it in a more organized manner but I figured just what popped to mind instantly was too much to put down so whatevs. Suffice to say, they went from a complex, unique, somewhat difficult at times gameworld and replaced it with a simple, generic, and nerfed piece of crap to pander to the casual audience.
On the plus side, the gameplay mechanics and physics in oblivion was way improved. No longer would you stand 5 inches away from some enemy swinging at them while the game tells you that you are missing them. And regenerating magicka made the wizarding classes much more viable (sadly it made them obscenely powerful so nothing could stand in your way at a relatively early/mid level).
Hurm....it seems after the oddly sedative combined peak, the dxm wore off quickly leaving me with typical post trip 2c-e stimulation.