I spent countless hours on Oblivion, but it was a heavily modded version, both in content and in mechanics.
I liked your review, it is fair and it highlights the good aspects of the game, but as a long-time player of the TES saga and a old school gamer in general, let me just say that Oblivion had more than one flaw. Most people found that the vanilla ( = non modded) version was quite boring and repetitive. I never really got bored of playing, I actually liked most aspects of the game.
What I found absolutely unforgivable was the mechanics of the leveling system, specifically the way it managed stats growth in relation to skill growth, and the enemy progression system. Let me explain.
The idea of skill growing with use is one of the most famous features of the TES saga, and it's one of those things that make you wonder "why doesn't everyone else follow their lead?". It's just so much more immersive to get better with something by doing that something. So I definitely have no complaint on that matter, and I actually like it a lot. The problem in this game was that stats only went up when you leveled up, and only did that in relation to every skill increase during that period of time. Let's say I need a boost in agility, I will need 10 increases in an agility-based skill BEFORE I level up in order to gain a +5 in agility. This means that, if I have a strength and endurance based melee warrior, I will probably have to STOP using most of my major skills and concentrate on every agility skill I have, and then I will have to try to level up only by using strength skills or endurance skills, or else I will have wasted precious stat points (i can only increase 2 stats per level up). This makes NO SENSE at all in my point of view. The entire philosophy behind TES is to get better at something by doing that something, and this system breaks that realism by forcing players to use skills in an unnatural way to maximize their stat gain. The result is that players used to create custom classes that made absolutely no sense from a roleplaying standpoint.
Second, I appreciate the world growing in some measure with the player, but this game was ridiculous. Bandits in full daedric armor with magical weapons makes no sense at all. Bandits are supposed to be bandits, rats are supposed to remain rats. Not every enemy encounter can be a question of life and death, you can't just force that on the player. It was boring as hell and made it all the more difficult to create an all-round character (you always had to use your best skills, so if you wanted to get better with a bow while you already were good with a blade, it was very hard to do so when you always met super-strong opponents).
Again, I loved the game world and I spent hundreds of hours exploring Cyrrodil, but I only did it once mods were available that substantially changed this two aspects of the game.