Nope, you're wrong on this one. Compared to Disney their attendance was small, but they consistently beat Busch and Sea World, even in the bad years.
2000
1. Magic Kingdom at Walt Disney World, 15.4 million (up 1.3%)
2.
Disneyland, 13.9 million (up 3%)
3. Epcot at Walt Disney World, 10.6 million (up 5%)
4. Disney's MGM Studios at Walt Disney World, 8.9 million (up 2%)
5. Animal Kingdom at Walt Disney World, 8.3 million (down 3%)
6. Universal Studios Orlando, 8.1 million (flat)
7. Islands of Adventure, 6 million (first full year)
8. Universal Studios Hollywood, 5.2 million (up 2%)
9. SeaWorld Orlando, 5.2 million (up 11%)
10. Busch Gardens Tampa, 5 million (up 28%) *
2001
1 - The Magic Kingdom - 14.7 million - down 700K
2 - Disneyland - 12.3 million - down 1.6 million
3 - Epcot - 9 million - down 1.6 million
4 - Disney-MGM Studios - 8.3 million - down 600K
5 - Disney's Animal Kingdom - 7.7 million - down 600K
6 - Universal Studios Florida - 7.2 million - down 900K
7 - Islands of Adventure - 5.5 million - down 500K
8 - SeaWorld Orlando - 5.1 million - down 100K
9 - Disney's California Adventure - 5 million - opened in 2001
10 - Universal Studios Hollywood - 4.7 million - down 500K
11 - Busch Gardens Tampa Bay - 4.6 million - down 8 percent
* "One of the big winners in 2000 was Busch Gardens Tampa, which saw its attendance sky rocket 28%. The park's early season promotion for Florida residents paid off. The park gave away a season pass to residents who purchased a full priced, single day admission. According to the park they made up for the lost admission revenue with increases in merchandise and concession sales."