The Civ franchise has been going mostly downhill since Civ 2.  It's hard do better than perfection, I know.   Civ 4 was not as bad as Civ 3, but still a bit of a disappointment.   Oddly enough it follows the same ranking as the first 5 star trek movies:  24135.   Here's why I hate Civ 5:

The interface has a lot of unnecessary bloat, yet lacks essential data.   For instance, instead of showing how much XP your warrior has when you select or mouseover your warrior, you first have to select the warrior THEN hover the mouse over his lame portrait to get that data in the tooltip.  Not that I agree with the MMORPGification of strategy game units in the first place, but if we have to do it that way then it would be nice to get a decent interface to display that data.

 The city interface is clunky and lame compared to all prior versions of the game.  It's like twice as many clicks to do whatever you want to do.    You have to enter the city screen and click twice before you can even start modifying worker allocation.   It no longer has hotkeys for inserting things at the beginning or the end of the production queue, and it no longer shows the partial completion status of things in the build queue unless they're currently first in line.   Worst of all, it no longer shows the build status numerically unless you hover the mouse over the stupid graphic.

Splitting the units into "multiple guys" graphically was a bad idea in the first place, but they went even further with it in this version, so that the individual soldiers are tiny and indistinct.

 Clicking on a city doesn't do anything.  You have to click on the huge nametag above it, which by the way, should have the production/growth progress bars horizontal instead of vertical to a.) make them easier to read an b.) waste less space on the oversized part of the tag that isn't actually telling you anything.

In the game setup phase when you are selecting a civ/leader, it shows the names of each civ's special units but no further details.   Unlike civ4, there's no way to click through to the civilopedia descriptions of these special units (I tried every combination of click, shift-click, crtl-click, alt-click, ctrl-shift-click,  etc and none of them did anything except plain old click which just selected the civ and exited out of the menu instead of anything to do with the specific unit icon I was clicking on).

 The voiceover is lame.  The intro cinematic is lame.   The game makes you enter 2-3 times at the end of each turn.  The game in general is typical laggy bloatware that you'd expect from typical modern game developers (who care more about superficial appearances of screenshots than having an interface/gameplay that actually works).

 There were so many little annoying design flaws that I couldn't stand playing the game for very long despite being a big fan of Civ 1, 2 and 4.