I've been wandering around playing lots of games with some weird settings lately and I have found that people aren't very careful about choosing the best nation for particular settings. So here are the nations I choose when playing some of the following settings:
- Diplomacy games: In these games, the fighting doesn't usually occur until much later in the game. People who attack early seem to just weaken themselves and get crushed in the end, particularly if an ally comes to help. In these games, I find that nations with a strong end game are very powerful. Russians are a good example. They are very strong in the info age and control vast amounts of territory. I usually pick them, their slow start doesn't hurt you that much in diplomacy. Greeks are also good. You can expect people not to attack for quite awhile and that gives Greeks enough time to become very huge. Egyptians can be strong because they have the freedom to build some key wonders, which can give them a good boost. Being first to get Colossus is helpful for fighting those end age battles. However, once the fighting starts, wonders are my first target with bombers and nukes. My normal favorite of Nubians are not so good because you cannot place merchants in territory of opponents with whom you are at peace. This negates their advantage. Mayans seem fairly weak, their strong cities don't stand up to well to stealth bombers and nukes. There is a whole psychology in diplomacy games, which is too lengthy to go into here, but you want to start off strong so people are a fraid to attack you and want to ally with you. But you need to be the stronger one at the end.
- Peace until XX games (team games): Generally the same rules apply as above. But it depends on when the peace ends. Bascially, you want to have a nation that is strong in the age where peace ends. I've seen peace until 30 minute games. These can be pretty boring; you can expect to be in info age before any fighting occurs. In this case I might go Russian, you can be Info Age with Global Prosperity in 30 mintues on most maps, and therefore Russians can be pretty strong. However, if it's peace for 10 minutes, you might want a Gunpowder Age civ like Chinese or Spanish.
- 2x (or more) starting resources: In these games I almost always choose Chinese. The instant villagers give you a quick boost enabling you to get an economy up really fast. Another popular choice is Egyptians because you can grab the good wonders early. However, I find that hurts you in the long run.
- End age is XX: In these games you just pick a civ that is strongest in that age. Modern Age = Germans, Gunpowder/Enlightenment Age = Spanish or Chinese
- East meets West: This map almost always seems to end up in Info Age. In this case Greeks seem very powerful because they can get to Info Age very fast, particularly if they do a SCI1, COM1 start and gater wealth from fishing.
- Big map, team games: I have not found any civ that can compare to Nubians in large team games (3vs3 or more). They just get a huge starting bonus from the merchants and that continues to snowball them into a monster powerhouse. Against the stronger end game civs, like Germans and Russians, you just want to attack them before they reach their power age. When playing against Nubians you have to raid viciously and attack them early or you are through. Boomed correctly, you can be info age in ~23 minutes or so.
Well, this is just my experience, which is slightly skewed because there are not a lot of experts in these games.