Do note that in your post you mentioned things that have aged well, and while I think it’s fine, they can feel a bit clunky, especially in comparison to some of the games heavily influenced by them (e.g. Dishonored, among others).
Edit: I’m mostly referring to direct melee combat here, and not the rest of the game. Truth is, you probably won’t find yourself using it much against humans, but the sword can feel a bit dated against some of the nonhuman creatures. And now that I think about it, Dishonored’s swordplay isn’t exactly super fluid either unless you’re countering and parrying.
You might want to add some mods just to touch some things up.
Also, while the second game is my favourite, don’t sleep on the third, especially if you like horror because one of the later levels is fucking incredible. I say all of this as someone who ordinarily hates supernatural-type horror.
And the third game also expands on the lore, which I like.
All of them are available on GOG and Steam.
Similar to Thief, the original Deus Ex is a great game which might also show its age a bit, but I think stands the test of time for the most part.