I love multiplayer, and play online all the time. It is true that too many people quit too soon, and that some regulars are annoyed by people taking over for the AI, and that plenty of people are real infants in the lobby (the 3.19 patch unfortunately broke the "ignore" option in Gamespy), and some other problems too. But MP gameplay is just so much more interesting and challenging than singleplayer that the latter just seems dull now.
The 3.19 patch was in general quite helpful, instances of games going "out of synch" have been greatly reduced.
Be aware that most MP regulars (myself included) will not even consider joining a game with a turn timer less than "blazing", or game speed less than "quick", or tech trading allowed. All other game settings are considered negotiable but not those three.
Also be aware that if you ever let the turn timer run all the way down without hitting "enter" during the first couple dozen turns, or more than once in a while after that, online regulars will quickly become impatient with you and will start evicting you from games they host. If you're at war in the game and hence have to take the full allowed time to enter your orders, by all means say so in the game chat so people won't start jumping on your case about being slow. Can't emphasize this issue enough.
A FFA game on a pangaea map will rarely take longer than a couple hours for the outcome to become obvious (i.e. all those remaining concede to whoever is dominating). But that's partly because those games tend to be played in a relatively crowded manner, i.e. 7 players on a small pang map with medium seas. Some folks like to host bigger, which means longer, mp games -- they'll usually say so in the game name (e.g. "Long FFA big map"). The most extreme form of this, which I personally no longer play because they take too damn long to get interesting, are FFA games on island maps where each player gets their own big island to build up on.
On a pangaea map it's largely warfare, but not just military: cultural warfare is quite relevant. My favorite mp FFA games are on the mixed land/sea map types, such as terra or archipelago, but it's crucial to remember that those map types are larger than pangaea. So a game on a small archipelago map will take a lot longer to resolve than one on a small pangaea map; hence I won't play in a game on a terra/archipelago/continents map set for "standard" unless I have several hours free.