NetFlix has it sewed up.
NetFlix will always be two steps ahead of Blockbuster. Hopefully NetFlix will upgrade the quality of their downloads, though. I don't know about the XBox downloads, since I haven't tried that yet, but the Watch It Now quality for computer is terrible.
In fairness, nobody “owns” the market, with Amazon and Apple as well as all the cable providers trying to break into VOD both Blockbuster AND Netflix are at risk from larger better funded companies trying to steal their video on demand marketshare.