I believe Mel Brooks ran out of steam by this point. There are a few jokes here and there that are funny, but for the most part, the film falls flat. It's definitely not a Blazing Saddles or Young Frankenstein.
"Hi! I'm Barf! I'm a mog...half man, half dog. I'm my own best friend."
I judge this movie on it's own merits..Comparing it with his past movies is like comparing an artists sculpture or painting based on what they did before. I don't know if it's valid to do that or not, I just prefer not to. I love Mel Brooks' movies, and I too have my favorites, but wouldn't say Spaceballs falls flat. It's just different than the movies he made with Gene Wilder, who starred in both Blazing Saddles and Young Frankenstein. Those moveis, had Gene not been in them, wouldn't be heralded as high as they are today, IMO.
Since Wilder had a lot to do with those particular films, I totally agree with your last statement. I tend to compare things sometimes, because I'm my own worst critic when it comes to my works. I always want to better myself and when I see a lackluster or just out and out bad product churned out by me, I trash it and start over. I can't tell you how many writing projects I have done this way.
It's easy to compare another's works to their crowning achievements, because you are supposed to seek ways to better your craft and to top what folks consider your best work. I don't believe Mel has done this with Spaceballs. Apparently I am not the only one who feels this way. When was the last major motion picture he had produced for the big screen? He's a comic genius, I grant you, but he hasn't been as great as he was with the films I mentioned before. It's very sad he reached his pinnacle over 30 years ago.