Here's the run-down for people who don't know TW games or have forgotten and are looking for something "good" from best to worst.
1) Medieval Total War 2 - largest scope(fuck Empire), best engine(screw warscape, evolution of RTW), best support, and best mods(SS, DLV, BC, TATW). Once EB2 comes out there will be no comparison even with RTW.
2) Rome Total War - Right now the best classical period game, because the base allowed for some great mods. RS2, EB, RTR. The scope is pretty good, there was a lot of support, expansions were decent. Just not as polished as MTW2(and less features).
3) Shogun 2 - Very polished, nice feel/art style to the game, great music, better AI(nothing that the bigger MTW mods haven't done however), etc. Unfortunately it's still Warscape, it's still the poor implementation of characters/family, silly tech tree, and relatively poor mod support. Mods are needed for a good campaign experience btw, if you want a challenging CAI and some more diversity.
4) NTW - ETW condensed into a size that can actually work, with a fairly stable game that looks good and does Napoleonic warfare somewhat well. Unfortunately it's Warscape again, and the small scope gets really old really fast. Would debate putting it below RTW2 because it's so limited, but unfortunately RTW2 is a mess right now.
5) RTW2 - Right now the game is a huge step back from RTW. All the things that seem to "expand" don't make up for what was taken away. Oh we have provinces and edicts now? Well who cares, because family tree and politics are severely limited. Oh there are Naval Battles? Well who cares because the "tech tree" and city expansion is pathetic compared to RTW. And the list could go on for some time, research it yourself. Oh, and it's a Warscape game(will never do melee combat well).
6) ETW - Everyone should know about this turd. It's still broken.
If you like fancy graphics in weak games, pick 4-6. If you like fancy graphics in a good game pick number 3. If you want passable graphics on the best, 1-2.
Seperate category for original Shogun and Medieval. If you like more of a board game feel, don't care about graphics, slightly simpler gameplay, but fairly well done, try them. The CAI can be quite challenging on hard difficulty, it doesn't have to think as much. MTW+ Viking Invasion is still on my HD and it was one of my favorite games for a long time. STW brought me to the series so mostly just nostalgia(although I enjoyed the heck out of it at the time).