There is no doubt Creative assembly are the best developer for "large scale" strategy game. (sorry for supreme commander fans).
I have played all the total war series (excluding some bad expansion), there is not pretty much innovation in gameplay only enhancement in graphics
(which is why medieval 2 score ranks lower than Rome).

However, they take a huge gamble by not progressing to titles like Rome 2, Shogun 2 (i'm still waiting) but create a totally different era than b4.
The colonisation age (from IGN, gamespy & gamespot preview), there is lack of melle units as opposed to its early games.
I will have no doubt they will push the map to a "huge proportion as well"
I will tell everyone what they are waiting for in this game (no not the graphics, sound, story.....etc) BUT the naval battle.

I love naval battle scenes (pirates of the carribean, master & commander), so this alone will push it for at least Top 5 games of the year.

What i really like about total war series is that you can really win even with odds stack against you.
Try play the historical campaign you will know exactly what i mean (ie : Hannibal campaign in Rome)
Its not bcos of the weak AI of your opponent.

This game requires you to use your armies effectively (positioning, manoeuvring & technic)
Its not like other genres :
1) Scale : it was big, as you control literally > 10,000 troops at a time plus facing the nemy of the same size (so no isnt everything)
2) Drawbacks : You will not always win with the same type of soldier. If you like to use heavy cavalry (very expensive) or war elephants
you will face crushing defeat if charge head on spearmen with phalanx formation.
Likewise if you use all spartan hoplites to attack your enemy, if they use cavalry archers still you lose.
It requires balance in every sort of way.

I have once face an enemy with odds stack against me (ratio of soldiers 1 to 3), but i literally beat them with clever manoeuvring with the cavalry
& infantry. When you look at the end of the game by "heroic victory", hardcore gamers will know how i feel or luckily scrape through with close victory.

Having said that, i was a bit dissapointed at some of the gameplay with medieval 2. It has gorgeus graphics & vast expansion but the scale was not
there anymore, hope creative assembly brings back the excitement of ROME which has garnered them so many awards.
I know its different era (colonization vs medieval) but creative has done that before, they can do it again.