It's not you having an opinion that's a problem. Having an opinion on what you have played is cool. But when you say blanket statement stuff like this:
"The SMS is a decent system, but the NES is something special."
"SMS games just aren't good enough on average, and there aren't enough great games on the system either."
"The Master System library is okay, but the NES library is outstanding."
... without fully exploring both systems' libraries, it doesn't look good. You rightfully don't like when people judge the N64 without having played enough of its games but you have done that with the SMS.