But, 15 Mbps is enough most of the time and 30 Mbps should be plenty for the more serious gamers trying to minimize lag. You are correct, Ping is very important, but so is upload, especially if you are host. Many ISP's offer a ridiculously high Download but much slower uploads.
Upload and ping are sometimes intertwined. You don't need much upload bandwidth, but you need to ensure you have a steady constant upload bandwidth. Apps like BitTorrent easily max out your upload pipe and compete with your gaming connection to the rest of the world. The steady constant upload stream is threatened, and introduces lag.
You can get by with very little upload bandwidth if you can carefully manage your connection.
My connection isnt alway constant it change every time I do a test from 8 to 11mbps and my upload go from 1.7 to 2.2 it still stay at 100% wireless strength but the speed are never the same when I test it
I can't really do that now I bought too many devices and I had to move to the Attic of my home so I put the router on the middle floor so everyone can get good range when they are online and I didnt want to much wires behind my entertainment center.
I recently upgraded my net to 105 Mbps download and 12 Mbps upload.
Believe it or not, the PS3's speed measurement is far from accurate. It reports values as accurate as drunk people throwing darts. My connection is 13Mb Down 256kb Up, and it reports as 2.3Mb down and 0.10kb up yet it performs well in online games.
What I would suggest is try a game that is network intensive and see the results.
Also note that at that speed, make sure your router is capable of serving that speed, and that you are on WIRED, not wireless.
Its 2012 an this problem still exists I have tryed,payed reserched this problem I have comcast 50Mbsec but doing a speed test with the units program or webbroser I only get 16Mbsec Every thing in my house is runing great 50Mbsec some times 60! (that includes my sons X-Box!) only the PlayStatons lag! But if I go on line players ar moving faster than me!