I spent a decent amount of time with AT&T 3g as my only option for online games (stupid work keeping away from home all hours). AT&T 3g before the loliphone for me in Houston was a consistent 30% packet loss and erratic reply times between 100ms and 300ms with about 700kb/s to 1.1mb/s. RF Online played perfectly. FFXI was playable with frequent dc. Wow was almost unplayable. Lineage 2 seemed playable but i would just drop dead for no reason every 30 minutes or so. Eve online was totally unplayable, unless you enjoy getting lossmails without ever seeing who shot you... After the advent of loliphone i canceled my AT&T account because packet loss jumped to a consistent 75%, reply times to 300ms+, and connection speed dropped to about 200kb/s. Everything became unplayable. Keeping in mind this was using a pcmcia 3g card, not tethering.
Now (only when i have to go mobile, thank Raptor Jesus) i have a Sprint 4g mobile hotspot. I get about 15% packet loss and reply times of 30ms to 90ms, and connection speed of 1.5mb/s to 4.5mb/s. After about 2 hours, connection speed drops to a consistent 500kb/s, although Sprint denies throttling. FFXI is totally doable, although i dc every 45 minutes like clockwork, and again Sprint denies resetting the connection. I don't know about other games because i quit everything but FFXI.
I no longer have 3g to test, but for me 4g in FFXIV beta is useless. I can't stay connected for more than a minute, and everything is extremely laggy. However, i'm playing on a laptop which only earned 1001 in FFXIV benchmark, so take with a grain of salt. On 20mb/s broadband i can play FFXIV at minimum settings with reasonable lag. And yes playing with minimum settings makes the game look like FFIII, the best game of all time. I won't be able to provide better information than this until ps3 launch because i refuse to buy another computer this year, soz.
Odd thing is, this stupid custom 18" vaio cost me as much as a used Honda and has no issues with CAD, Maya, 3DS Max, or batch video encoding jobs. Makes me mad as **** i have to play a mmo of all things at min settings after only 9 months. But i guess i should have learned my lesson a while back after an alienware aurora sli laptop could not play AoC or WAR after only 5 months. One of these days i'll learn to stop buying laptops. :( Although, alienware sli laptops do make lovely paperweights...