Since you asked so nicely...
First of all, I don't do a "10 best" list; I do a "ten favorites" one. I use the cop-out that I'm simply not qualified to judge the year's ten best comics, since I don't read nearly enough of them to judge properly. With that out of the way, though, I have fun doing some heavy thinkin' on just why I like those ten comics so much, and usually come out with a better appreciation of them than I had going in.
Anyway, here's what I set down for last year's group:
"1. The comic had to come out in 2007. For ongoing series, that's self-explanatory; any book that shipped an issue from January through October qualified. Limited series that shipped more than half their issues in 2007 also made the cut. For trades, it was a bit tricker. Obviously, trades released before this year that I didn't read until now didn't count, nor did trades collecting "classic" material. Some trades that shipped this year, though, collected mostly material from last year. Two of my favorite series, Fables and Y: The Last Man, only shipped one trade in 2007, both of which mostly collected material from 2006. That's why they're not on this list.
"2. I had to have read it. Duh. This disqualified Wonder Woman, since I haven't read most of the issues it published this year, and I can't really endorse Jodi Picoult and Allan Heinberg's work based on how much I liked Gail's, can I?
"3. I had to have paid for it. I read a lot of comics this year through loans from friends or in Barnes & Noble. But if I didn't eventually buy it, I obviously must not have thought it was very good. Some I did think were OK, but "OK" doesn't translate to "favorite."
"After that, it was all about cutting the list of comics I read down to ten. I could have gone farther. Some books had great writing, but lackluster or inconsistent art. (The frequent shifts and fill-ins on the X-Books disqualified Mike Carey's X-Men and Peter David's X-Factor, both solid mainstays throughout the year.) With others, I went with one book by a certain creator over another. I tried to be fair and well-rounded, or as much as I could be given my admittedly limited intake.
"In the end, I came up with six DC comics, three Marvels, and one webcomic that represent the most fun I had reading comics all year. I think that's a pretty good rubric. So, ten days left in the year, ten entries. In alphabetical order, my Favorite Comics of 2007. Regardless of whether or not you enjoyed them as much as I did, I hope you enjoy reading about them as much as I enjoy the writing."