Yes, "Smelly Cat" from Friends was the best song ever written, because it is funny. I've taught my kids the Smelly Cat song, so it is living on for future generations. Phoebe did a great job of singing it too. It also makes a point, that a cat needs to have a good responsible owner, because otherwise they will smell because of what they are being fed.
It is to my knowledge that "Smelly Cat" from Friends is the best song ever written. It has a well-written chord structure, and is written by the lyrical mastermind herself. not to mention that the performance in the coffee shop was none to go up against. I believe that "Smelly Cat" should have made it onto a Billboard Top-50 countdown.
Of all the songs, Smelly Cat is one of the most well known out there. You just need to say the words and everyone around you will know what it is. This is partially to do with the fact that the series is so successful and well known, and partly due to the catchy lyrics and relevant topic. Animal right topics are so well publicised now that the message is very global.
Let's face it: "Friends" is the biggest piece of crap TV show on the planet. Yes I've seen bits and pieces of them. Unlikable characters, douchebags reminiscent of sports douches, arrogant. "Seinfeld" is a much better show than this piece of s--t. "Friends" is the most unlikable show on the planet.
"Smelly Cat" from Friends was not the best song even written. To say so, would be an extremely bold statement. It was definitely a defining song for the show in that it was very memorable. However, it is not a song that is considered a part of the music industry or a part of music history. It also is not a song that was not that good.