Hmm, yes, I would say it's the best in the last 5 years*, but best ever… well for one thing it's just too early to make that call. I would want to complete a game like the 2 or 3 times and let it sink in a bit, let the 'new game euphoria' (I like that term, and it's so true) calm down a bit, and think it over.
*Actually, I just checked, and Bloodlines' fifth aniversary was just a few days ago, so it sneaks in as being within 5 years of DA, so that muddies those waters just a bit for me. You'd be very, very hard pressed to argue that a rough gem like Bloodlines was a *better* game, but in terms of enjoyment… Well I've played Bloodlines 4 times to completion and few other times to muck around with some things.
Anyway, big call. Just that people can reasonably consider DA:O for this title says plenty. Definitely top 5 for me, anyway.