Studio of the Year: Warner
Mainly because of their excellent support of OAR in 2004. Also, this year, the first-ever OAR home video releases of Around the World in 80 Days and The Wrong Man occured. Also, the SE's of Blazing Saddles and The Iron Giant dropped the pan & scan flip-sides that were on the original DVD's. The "That's Entertainment!" films featured both 4x3 and 16x9 transfers, which allowed those with both monitor setups to see the films in the best way possible. Both the CinemaScope and flat versions were provided on the Seven Brides for Seven Brothers SE, both 16x9.
More importantly, they do dual releases when they do P&S DVD's. So, no one is let down with the release of Scooby Doo 2 (even if they're let down with the actual movie

) They're also not doing what Columbia is doing: taking the dual-sided DVD's and re-releasing them with only the P&S version for retailers like Wal-Mart. On the Tom & Jerry 2-disc set, despite problems with other cartoons, they created brand new 16x9 transfers of the 3 CinemaScope cartoons.
Even above that, they're one studio that you simply can rely on OAR to be on DVD. There's none of the guesswork that people put up with for Universal, Columbia, or MGM.
I would like to mention that Fox and Paramount have supported OAR since day one, though. They've been a great help to making widescreen popular.
Most improved: MGM (barely)
Mainly because they cancelled the Techniscope (2.35:1) film, Charly from their schedule. This is part of the ABC Films licensed package from Disney. The DVD was to be released in October with a pan & scan transfer and no extras. Thanks to the efforts of Chris Blig and possibly Cliff Robertson (who was shown the petition and was alerted), there is no P&S DVD of the film in stores. However, with MGM to be with Columbia, let's hope it's not brought out again only to be unchanged. MGM is capable of great work!
Worst studio: Columbia
I think everyone else has been perfectly clear on why Columbia is being downright insane with their product. Instead of repeating, I'm just going to agree.