I'm with David. Depends what you mean. For me, the answer is easy, the Toshiba XA2, which is the most expensive one of the bunch. Its better than the most expensive Denons ( non HD-DVD) as well as the Oppos due to close to the best you can get in video processing hardware. The A35, its 3rd generation highest player, has better audio firmware but gives ground overall on the video side to the 2 nd generation XA2.
I just bought the Toshiba A3 and for the money (300 bucks, and 2 free movies) it seems to be a pretty good value. So far it has played everything I've thrown at it (knock on wood).
For the OP I will say the HD-A3--Toshiba's current entry level HD-DVD--is the best buy. AFAIK, its two drawbacks are lack of 1080p output and no multi-channel analog audio outputs.
The lack of 1080p may not be importent, depending on the TV one uses the player with. I am a little disappointed about the audio outs as I won't be upgrading to an HDMI 1.3 receiver anytime soon, so I'll be stuck with plain old DD 5.1...or is DTS the default on the optical output?