ETW is lightyears ahead of RTW. At least in my opinion, RTW was the low point in the series. The introduction of a 3D game without the programming behind it to handle it.

ETW has essentially fixed all of the problems related to the transition to 3D and the new campaign map. Many other aspects of the game have been streamlined (like diplomacy) or expanded on (like trade). I've also noticed that the in-game tool tips are a lot more helpful and there's a lot more details available in the interface than there used to be, so that may excite the nerd in you.

ETW's biggest problem, as always, is the AI. The diplomatic AI has been acurately described as the Black Knight from Monty Python's Holy Grail. It's very stupid in that it constantly makes decisions that are not in its best interests AND are very irksome to the player. The campaign map AI is vastly improved from RTW (no more headless, 1-2 unit stacks randomly roving around the map for years) though it's no strategic genius either. I can't really comment too deeply on the battle AI. It's better than RTW I think. I don't really remember M2TW much at all anymore (a pity really)