Comedies are tough, because they are usually making cultural references that don't make sense 10 or 20 years later. That fact highlights the brilliance of Caddyshack and Airplane, which are still hilarious 30+ years later.
I am also willing to give older movies a pass on special effects, to a point.
More:
Towering Inferno - this POS was nominated for 8 freaking Oscars, including Best Picture? This movie is what would happen if you set the Love Boat on fire, except the Love Boat is less cheesy. The movie also rips off the Poseiden Adventure. It is just freaking terrible.
Broadcast News - saw this in high school, and I thought it was so deep and insightful. I also immediately identified with the Albert Brooks character and thought Holly Hunter was adorable. The movie is still OK, and maybe even worthy of some of its Oscar nominations, but not an all time great. Holly Hunter is annoying and chews the scenery, and Albert Brooks character is just a -hole. Why is Hunter even conflicted over Brooks? Finally, the William Hurt character seems much more appealing in hindsight. He tries to help Brooks even though Brooks is mean to him, and he is basically just a nice guy throughout the film. Finally, the big turning point, doing a cutaway reaction shot and fake crying, seems quaint by today's news standards.
Forrest Gump - How the did this film beat out Shawshank Redemption and Pulp Fiction for an Oscar? Forrest is a fun, feel good movie and Hanks does a great job, but the movie is emotionally manipulative, Jenny is just a terrible person which creates plot problems for everyone's motivations (wouldn't Forrest's over protective mother have slit Jenny's throat before letting that succubus near her son?), and a big part of why the movie won a statue was the special effect of splicing Hanks into scenes with historic people, something that every high school AV department could do within about 5 years of that movie coming out. Pulp Fiction and Shawshank are two of the best movies of all time, and a case could be made that even Quiz Show was more Oscar worthy.