Don't worry about that, we're happy to see content like that

Since for most people it has been a very long time since the first time they played Unreal, it's always interesting to see the reactions of other people playing through the game for the first time!
As Buster mentioned, due to the nature of Unreal, you can extend the game a whole lot by the current developments, namely patch 227 that brings stability and visual improvements, and most of all, S3TC textures from
http://unrealtexture.com/ (from the screenshots, it seems that you're not using them - try it, and you'll be surprised to see how the game really looks

I do believe that no other game in existence has that detailed textures!)
Veteran nitpick: "Unreal III" should be "Unreal Engine 3", since "Unreal III" is the name of the third game in the Unreal series (currently doesn't exist, but might very well exist in the future!).
You don't just get a sniper rifle. You get...umm...well, ok, you just get a sniper rifle, but it's more fun to fire than most other sniper rifles, and has the added advantage of being able to blow off enemy's heads.
Heh, funny you should mention that - originally the alternative fire of the Rifle was to shoot three bullets at once

They removed it in favour of the zoom function, however. But yes, Epic did put a lot of work into the unique design of the weapons. All of those things you mentioned there they called the "Unreal twist". They added crazy modifications to the vehicles in UT2004 in a similar vein.
For instance, the enemy designs: they're just...well...bland. I can't think of a single enemy that didn't look like it was ripped from somewhere else, and some types look so identical that you'd be hard-pressed to differentiate them from one another without a side-by-side comparison.
Again funny you should mention that, since historically most enemies were in fact inspired by movies, so they are kind of ripped

And yeap, to this day I can hardly tell the difference between Skaarj Assassins and Skaarj Lords, for instance.
2 levels in particular (the Na Pali Haven and the ISVKran) were significantly less engaging than the rest of the game, the former featuring far too many dark uninteresting corridors, and the latter having combat that was far too easy and several areas that looked inviting, but were actually inaccessible.
True that, too. ISV Kran, in my opinion, is the most bland portion of the game... Very low visual variety, and even very low musical variety. It could have done without decks 2 and 3 and it would have been better...
As for Na Pali Haven, yeap, the Krall are surprisingly easy. They are not any harder than Brutes (most of the time easier). I'm not sure why that is (I think originally they were supposed to be more difficult to deal with?)
Agreed about the inventory items, too. I hardly ever use them, even the Amplifier.
About RTNP: Here's some history. It was created mostly from the unreleased Beta material of Unreal - that's why some parts are somewhat unconnected. And it was made mostly by a part of Legend Entertainment rather than Epic Games themselves. Mind you, they also made really good games like The Wheel of Time and Unreal II, so I know they could have done better here as well, but I think they just didn't really try too hard. That also shows in some of the coding (you noticed how awkward the Marines are - their coding really is odd). Though personally I liked a few things quite a lot about it - mostly the Cloak pickup (multiplayer only) that is invisibility done right + infinite jump boots, so it's super fun to use it. And the Combat Assault Rifle that shoots from both barrels at the same time, making it really something else (although I'm not sure that it was intentional!).
So yea, overall that's how I feel about the game as well. An interesting read there!