What you did get is:
1) improved graphics
Debatable.
Flat-out wrong. Alt-clicking to upgrade all units got broken and never fixed, half the time it doesn't read Ctrl-clicking/Shift-clicking on units, Vassalage breaks a person's ability to read diplomacy, and TMIT can tell you about the rest of the problems with the BtS UI.
3) fine tuned some of the small and big flaws in vanilla and Warlords. Things like staggering unhappiness and unhealth early on and brutal war weariness
In return for introducing brand-new flaws. Espionage as a whole springs to mind, also, teaching the AI to use Slavery instead of fixing the entire broken mechanic.
4) Great Generals - started in Warlords expansion. You are really missing out on this one. Simple feature and lots of fun. Earn a Great General and you can create super units with access to otherwise unavailable promotions like Medic III and Leadership (boosted XP)
Thus putting the game on even more of a Warmonger focus.
5) Improved forts...they do much more like create canals and ports
That doesn't mean they'll be built.
6) Pretty much all the mods are for BTS including the highly recommended BUG mod that improves the UI and advisors.
And this is supposed to persuade somebody who's content with Vanilla how? "If you buy an expansion, then you can alter the game
even more, even though you've just said you don't want to alter the game!"
7) Better conversion of hammers to wealth and research
If you're in to that sort of thing, I suppose.
8) Corps actually are very cool and powerful despite what is said above, but you can just ignore them and use good old State Property, which is simply and powerful - and also boosted in BTS
and so on
Yes:
8) Espionage forces you to constantly rebuild the same tiles with your workers as the AI spams spies.
9) Slavery is still broken, but with this version, the AI uses it, pretty much forcing you into a Civic to stay at parity. This is a design flaw.
10) The Space Elevator was made worthless.
11) Vassals are still broken.
12) Random events that have a possibility of screwing you over are not the way to balance broken civics.
13) Corporations are not balanced against each other.
14) Stiff overseas maintenance penalties.
15) Holy cities lose their spying abilities.
BTS is the reason CIV IV is one of the best games of all time and best of the Civ series.
No,
Civ IV is the reason Civ IV is the best of the Civ Series. It was the first to not punish you for building infrastructure and the first to actually punish you for REXing. It came closer than either of the expansions to making the game balanced between warfare and peaceful play. Warlords and BtS have their appeal, but their enhancements are matched by their induced limitations and pitfalls.