No way in hell was Davenport best player in 04 or 05 IMO. 2004 she didnt even reach a slam final. Henin despite her limited schedule due to health problems, and her official YE ranking of #7 making sense, I would say was best player. She won the Australian Open, Olympic Gold, Indian Wells, and 5 titles overall, which is still a better year than anyone else, despite playing only 50% of the time. If it was not Henin it would be Pova who won Wimbledon and YEC, beating Serena in the finals of both. Maybe with her year round consistency I might go with Lindsay if she won a slam, or atleast won a secondary big event, but she didnt even reach a slam final so no. 2005 was Clijsters.
I think Justine has a very good case as best player of 03, 04, 06, and 07. I do think it would have been Serena if she didnt get injured, but she did, and it still would have been Serena if she won that French Open semis, but alas it is what it is. Even if you disagree there is no doubt Henin was by far the best of the overall 2003-2007 period and it isnt even close:
Henin- 7 slams, Olympic gold, 2 YEC, 3 YE#1
Serena- 4 slams
Sharapova- 2 slams, 1 YEC
Mauresmo- 2 slams
Venus- 2 slams
Everyone else- 1 slam or less each
Again not a Justine fan, but giving her, her proper due. Serena and Justine fans are the equivalent of Graf-Seles fans. Both are on such extreme sides of reality regarding both that they will never reach any kind of compromise. Largely due to the deep impassioniated dislike both sides have for the other.
On the other hand I personally think Justine is a huge coward for quitting due to a 6 month slump (early 08). I do think if she toughed it out she would have eventually started playing well again. Slumps happen, burnout happens. It was pretty laughable to quit right before the French when even in **** form, getting bagel sets from Serena and Maria on hard courts, she probably still had a good shot at winning given the weak clay field. She could have then taken a break for a couple months, and missed Wimbledon which in subpar form she wouldnt have a shot at anyway. Vanhool made a good point how Venus, Serena, even Sharapova, fight through all the up and downs, and take their lumps and bruises. Justine obviously does not. Then again she isnt the only one including some champions greater than her (eg- Borg).