Top grossing movies since 1990:

2003: Finding Nemo
2002: Spider-Man
2001: Harry Potter and the Sorcerer's Stone
2000: How the Grinch Stole Christmas
1999: Star Wars: Episode 1- The Phantom Menace
1998: Saving Private Ryan
1997: Titanic
1996: Independence Day
1995: Toy Story
1994: Forrest Gump
1993: Jurassic Park
1992: Aladdin
1991: Terminator 2- Judgment Day
1990: Home Alone

Most popular movies since 1990 (as tallyed by imdb.com):

2003: The Matrix Reloaded
2002: The Lord of the Rings: The Two Towers
2001: Shrek
2000: Gladiator
1999: Star Wars: Episode 1- The Phantom Menace
1998: The Truman Show
1997: LA Confidential
1996: Fargo
1995: Se7en
1994: Forrest Gump
1993: Jurassic Park
1992: Reservoir Dogs
1991: Terminator 2- Judgment Day
1990: Goodfellas

The most popular movies list is skewed because it's done by imdb readers. And of course, people who read imdb are not representative of the American population.