You won't get the speeds you need for online gaming from Verizon DSL, but Fios is another story. Stick with Comcast (as much as it sucks), until you can upgrade to Fios.
I had Comcast for a few years. I didn't have any complaints until I got my 360 and really started gaming online a lot. Comcast service tends to spike up and down, so you'll have a great connection one minute, and you'll get dropped out of the game the next minute. Now that I've switched to Fios, I haven't had that problem, and everything is running fast and steady. My only problem is I can't get my DS to work with the Verizon router, and the Nintendo Dongle freezes my computer up for some reason.