Are you sure that's Sonic Team? That seems more like Sega's philosophy of "if its sales, don't fix it"
VF has gone through several changes since its inception and so has many other titles.
Not really. Virtua Fighter has stayed pretty close to home the entire way through. The only big deals I can think of are being able to expand or contract the arena in VF2, the evade button in VF3, the loss of the fat man in VF 4 and that's about it. Other than that, some serious tweaking, and the addition or occasional removal of a character, Virtua Fighter has been pretty damn close to the same game since 1993.
Now that's not a bad thing. And Sega has always used Virtua Fighter to showcase their capabilities, but the series is hardly what one would call daring or risque.