Empire wasn't so buggy after that initial teething period. I think the main problem with Empire is the base concept. I mean, there's a reason nobody bothers to make games based on World War I. To say it would not be as interesting as a World War II theme is an understatement. Empire is not that bad, but it's hard to compare those gritty, foggy battles fought by inaccurate line infantry hiding behind logs with the grand old days of knights in shining armour, or for that matter, samurai and Roman legions. Most people have pretended to have a sword fight (or be a ninja) at some point; fewer would say they have reenacted the American Civil War.
Aspersions aside, Empire is a great attempt to push the franchise forward. Previous games are without an explicit tech tree, an active trade system, multiple theatres or different forms of government. It's an interesting period of history, the time of the American revolution and the powerful East India Companies; as a result, it is the first Total War to feature the subcontinent. Combat is vastly different from the other games with its abundance of gunpowder and slow moving artillery. Fine control over positioning becomes vital and there is a cover system. Defending troops can hole up inside a building or sandbag their position. Ideally, it could ask the player to think carefully, but the greatest downfall of the game is that the combat theatres are so repetitive.
The highlight of Empire is the sea battles, again a first for the franchise and I'm not sure I've seen any game really attempt anything like it. As faithfully rendered as the mighty tall ships are, it's even better to see them smash and shatter from cannon balls. Suffice to say, there's a lot to the game that is easy to gloss past. And I suppose it's arguable that should combat not be to sir's liking, sir can completely ignore the RTS side of the game, playing the campaign as if it were Civ.
Shogun 2 takes a step back in time and is set entirely in Japan, yet the scope and ambition of Empire is not lost. You can still see all the little things they've retained. Empire is like a reckless child, the sort of game that you're not surprised to be disappointed by, but nevertheless you can't stay made at, because at least it gets in and has a go. Current shooter franchises could stand to draw some inspiration from it.