I also enjoy the show and books. Theres a youtube video of Martin saying he enjoys the changes and just wants to watch good television. There's a pretty good clip of him of him using Gone With the Wind as an example, saying the film was different than the book but both were great.
Altough I do agree about the bit with them choosing an incomplete series. Not that it bothers me if say the show wildly diverges, but because I do agree there are other awesome fantasy series out there and I'm curious why an incomplete series was put on the table. I imagine it has something to due with the budget, because the only excuse I can think of is how expensive it might be to bring trollocs, dragons, orcs, shades, or a huge abundance of magic to the screen. The first season or two of GoT was on the tame side as far as extravagance was concerned. Entire scenes are just dialogue yet it works because the dialogue and characters are so great. They just happen to be in a fantasy setting. As far as fantasy series go, most of what I read does tend to be a bit over-the-top with things I imagine would cost an arm and a leg to bring to the big screen.