Dortmund are actually well known in the UK to people who know what they are talking about, and they are revered as a formidable team, but obviously more so.
I suppose your issue (and it's mine too) is that people only watched these games because Real were playing, expecting them to beat ze Germans and then become a BVB fan overnight.
In regards for throwing a Chelsea shirt for a BVB one that's a great first step to being a PROPER football fan.
Majority of the top clubs in any country now are just money machines, there are only a few that are driven by the passion of a victory, rather than the financial benefit.