Hello, I am aware that this is an old post, I stumbled here while looking for 9:4 ratio (namely 3600x1600 or three 1600x1200 monitors flipped on their side.
But as for the original question, games from 5 years ago and older were rarely coded for supporting wide resolutions, so, if you are to play BF1942, Call of Duty 2 or SWAT 4 extensively, you may be better with a 4:3 or 5:4 ratio (5:4 is the ratio for 1280x1024 screens, usually 17 to 20 inch only).
Newer games are mostly coded with 16:9 in mind (since a lot are direct ports from consoles) the FOV is usually engine dependent but mostly, they adjust correctly for the appropriate screen ratio, I tried 2600x400 once on an UE3 based game and the FOV scaled accordingly, I could see nearly 360 degrees.
16:10 is a better choice if you work on a lot of documents (it can scale two letter format pages side by side) and 16:9 is the best choice for entertainment (movies and games)
As for my original statement, three 4:3 monitors on their side (flipped in portrait mode) would give a 9:4 ratio which would be awesome for vehicle games (racing, flight...)