To make bold statements such as this, one must first have data for which to justify the statement. Without delving into the legality dilemma, I would have to say there are things out there that can compare the the ECA stack, and perhaps even outperform.
As for your question, I think you've answered it, implicitly. If the other fatburners were as strong as ephedra, they would be banned. Why don't people buy ECA? Probably because it is banned. For example, to get it in my state, you are limited to so many mg's per month. When you purchase, you must shown identification, and sign a waiver. This waiver is then sent to the DEA for documentation. If you go over your limit, you get a visitor. Remember, this compound is also used to make illegal drugs.