I'm on a quest to purchase and drink every oktoberfest beer in my market.
So far I've had Warsteiner, Spaten (year round availability unlike most), Brooklyn, Magic Hat, & Sam Adams.
I've had Flying Dog's Dogtoberfest (good) and Summits Okto, also very good. Just not from this years batch. I need to get those. I have to find Erdinger's and I *think* Ayinger has one as well.
So far my favorite is Brooklyn Brewery's variation but I do think Sam Adams is a good one.
Summit and Flying Dog is very high on the "gotta have it list".
fwiw New Belgium has a Hoptoberfest that is out, and as the name states its hoppy, nothing close to an oktoberfest beer (bier) like you would think. Decent enough though.
(If anyone has something odd in their market I can't get in DFW let me know and I'll swap what I can get that you can't)