Someone in another thread had an idea that we have lists already made up for any potential map; i.e. one for Panagea, one for 'pelago, one for continents.
So here is my take on a archipelago map. Seafaring is one requirement. Therefore looking at the seven civs with that trait:
Portuguese (Expansionist, UU- Carrack (2.2.4)) - Just about the worst choice we could make. The Expanionist trait is not good for islands. And the carrack is not exactly a game changing unit. Grade: F
English (Commercial, UU - Man O'War (4.2.5)) - IIRC, the MoW can also enslave. You have the ability to control the sea completely. Commercial trait can be powerful. Grade: A
Carthaginian (Industrious, UU - Nu Merc (2.3.1)) Industrial is one of those take it or leave traits for me. Yes, the faster worker makes a difference in the early game, but I don't know if that will make a huge difference against humans. Grade: C
Vikings (Militaristic, UU - Zerk(6.2.1)) - This is another game changing UU. The increased odds of leaders is always nice. Grade: A
Spainish (Religious, UU - Conquistador (3.2.2)) The all terrain as roads is a nice feature for a UU. Makes an enemy really protect their entire front.
Grade: B
Byzantine (Scientific, UU - Dromon(2.1.3)) - The early bombard feature on the Dromon is great to have, especially on a 'pelago. Grade: A
Dutch (Argicultural, UU - Swiss Merc (1.4.1)) - Argiculture is a great trait, except you won't have many rivers on a 'pelago. The UU is a nice unit Grade: B
So I would say:
1a. Byzantines
1b. English
1c. Vikings
4. Dutch
5. Spanish
Next, I'll look at Panagea civs.