I know what I say will probably be an unpopular view however, I have never been a huge fan of Tango. It is cheap and cheerful, especially if you have the menu del dia. Yes, the waiters are very kind and remember you but can't say I ever thought the food was that great.
I think you are probably right in saying the location helped its popularity. Since it has moved - despite being extremely close to us - we have not visited it.