Where can I input a stock ticker and get back a list of the top 3-5 competitors of the stock? E.g. if I input F, I get GM, etc. It would be great if this could also give me data for delisted stocks.
Sure: Thompson Reuters Eikon and Bloomberg.
I guess you are asking for a free version of this and it this point I have to say to the best of my knowledge that there is no such service.