I was a Nintendo only fan but am now a fan of both Nintendo & Sony as I own a Wii U & PS4. I also like the XBox but I just became a multi-console owner so baby steps
Nintendo has many IP's which I grew up with and still like today. They are also the only one currently focusing on local play which I like a lot. They try to bring new things to the table with their consoles and while I'm not the biggest fan of the Gamepad I applaud them for trying
I'm new to Sony but I do appreciate that they have many new IP's each gen. Nintendo does too but not nearly as many. I also am no graphics whore but like that they try to be more current with their consoles in the power department. I'm learning their style but am enjoying every step