For me, the biggest way that RTW lets me down compared to the other two is that when you take an army into battle after looking at theirs, the odds, the experience etc is that you know beforehand what the result will be and most often if not always (unless a brutallt stupid AI bug such as general suicide with reinforcements) you know you will win.
The only thing in doubt is how much you will win by and if the enemy army will still exist post conflict.
Someone mentioned build up of tension previously on this thread and that is the key element that RTW misses. RTW is more like taking a Dyson vacuum cleaner over Europe and easily sucking up enemies, especially with the AI not doing to you what you can do to it ( as effectively) such as assisinations, building up and using diplomats to bribe etc.
I remember in MTW taking my stack of 1000 well solid troops with an awesome general against many thousands, lets say 4000, and having an EPIC.
Due to tiredness you would have to keep a couple of units in reserve until later but would that mean you would be too badly outnumbered. OK i've killedthe general quick, that leaves only 3800 troops to deal with vs my 950.
This type of tension no longer exists in RTW and was a real draw for me in the other 2.
I PREDICT A POST WILL FOLLOW THAT SAYS 'I THINK THERE IS THAT TENSION IN RTW AND I AM JUST NOT PLAYING IT RIGHT' Hmmmm, how long will it be.?

By the way, hello all, haven't posted in bloody ages.