I wouldn't call Biker Mice From Mars a ripoff of Teenage Mutant Ninja Turtles, per se, however, BMfM definitely owes some credit to TMNT as it's one of several human sized anthro shows/products that came in the wake of TMNT's success (See also, Street Sharks, Battletoads, Snailiens and Adolecent Radioactive Blackbelt Hamsters).
I've heard some people say that Biker Mice from Mars was boring, but the fact of the matter is that I've never watched the show long enough to get bored. Based on what little I've seen of BMfM, it just struck me as being a fairly standard "alien mutant anthros in human" world scenario. The key difference was that one of the Biker Mice apparently had a potential romantic thing going on with a human woman, which quite frankly, strikes me as being both implausible and a just a wee bit on the creepy side. I mean, how badly have men worked you over when a 6 foot tall alien mouse seems like a good prospect to you?