Woody is fine-crafted, hand made, rag-doll from the 1950s made with loving care to tie in with a beloved children's TV show. He's meant to be a child's pal and loved toy that can last for generations.
Buzz is pop-trash, in one year out the next, TV-show tie in intended to make bank for some company and he was made in China by machines. In short. He sucks as a child's toy/loved play thing.
Buzz is meant to serve a purpose and void to help a company make money and just to get the consumer masses to shell out $20 for a cheap piece of plastic with easily removed shitty stickers, visible screw holes, a cardboard box for a "spaceship" and crappy sounding audio effects. Buzz is a piece of shit and an example of modern toy-making. Slapped together product with no real "thought" in it.
It's only through Woody, a hand-crafted toy intended for years of use and love, that Buzz is able to become a "better toy" and connect with Andy and the rest of the other toys.
It's a symbol of what toys have become, it's probably a pretty good bet that most of the toys people my age had are in landfills or a box in the attic as the pieces of plastic they are. If they were kept and put on display it's only because they "looked cool" with maybe a touch of sentimentality. It's more likely any toy you kept was a toy like Woody as it's got some "connection" to it with a semblance of heart and reality. I've got a Bert (from Sesame Street) doll I had when I was a child that I loved and I still have it! It's sitting on a bookshelf in my bedroom it's a reminder of my childhood. All of my Ghostbusters and TMNT toys that I played with all of the time and had a ball with? They're in a box in my parent's attic.
That's why Buzz "thinks" he knows who/what he is and Woody knows he's a toy. Simply put, Woody is a better toy than buzz is, as are all of the other toys (who apparently always knew they were toys as the way Buzz acts and behaves in the first movie they seem unfamiliar with.) They're all classic toys that people assign emotions too. Buzz was a plastic piece of shit whom Andy only cared about because, as I said, Woody made Buzz a better toy through the process of the first movie.