Aside from Bavaria, another region of southern Germany rates pretty good for beers in my view. That would be the state of Baden Wuerttemberg.
Two of the most well-known beers are from the state's biggest city, Stuttgart. Those would be Dinkelacker and Stuttgarter Hofbraeu, both of which by own tasting experience many years ago were pretty good. (My old army sgt pal, who is an American descended from the state, disagrees as as to Dinkelacker, however.)
Dinkelacker also produces Schwabenbrau, which I like.
Here is one that I recommend-from Karlsruhe. It is Moninger Ratshernn Pilsner.
My experience with this beer goes back to the early 1980s when we were visiting friends in the nearby village of Bad Herrenalb. This one was the best I found in that area. The local beer of Bad Herrenalb, Monch's Klosterbraeu, was also pretty good.
The only beer I am aware of in Heidelberg is Engelbrau and only because I have a mug of theirs. I don't know how good it is or about any other breweries in the city.
As for Freiburg, I only ate and drank beer there for lunch one day, and I recall being somewhat disappointed in the beer. My friend, who studied in Freiburg, says the beer there "sucks". I wouldn't be that harsh since even the disappointing brews to me are good.
I should comment about Goeppingen, where I spent the first couple of months of my army tour in Germany before moving to Erlangen. This is where I started drinking beer-at a local beer fest. I don't recall the brands and actually didn't get off post that much. It seems the big brewery there was Staufenbrau, which apparently moved in 1996. Here is a page that also lists other breweries in Baden Wurttemberg.
A couple of local Goppingen breweries I found on the internet are Kaiser Brau and Lammbrau Hilsenbeck.
All in all, if you are traveling in the region, I don't think you will be disappointed in the beers there.