I'd say its
Angel > Firefly > Buffy> This Dollhouse pilot
If we break it into chunks
Meat of Angel > Early Buffy > Firefly > very start of Angel > Dollhouse pilot > middle years of buffy > last years of buffy
I'm not a Whedon fanboy, in that I follow any Whedon net sites or the subculture of Buffy or the fanfic travesties, but I have certainly enjoyed some of his shows. My worry is that he thinks he's a feminist, but has horrible female leads or major female characters, and then does things with his female characters that make them completely pathetic and compromised. Angel was probably stronger because he had to deal with a male lead, and Firefly stronger for the same reason. Also, even though Firefly revolved around a buffy jr character, she was more a narrative device than a strong character that overtook episodes. Whedon makes interesting nerdy hot chicks that provide good subplots. Once he goes with focusing on the female psych, shit falls apart and you hate his shows.
Dollhouse and Eliza Dushku as its main focus seems doomed for those reasons.