As for how I would classify legs....if the movie hangs in the top 5 (Good Luck) on August 20, I will say it's got legs. That's my opinion and I'm sticking to it.
How about August 21, lol will that work enough for you to join the rest of the world lol?
http://www.boxofficemojo.com/daily/chart/?sortdate=2003-08-21&p=.htm
1 Freddy Vs Jason $2,207,000 -12% $48,044,640
2 S.W.A.T. $1,713,149 -2% $77,265,738
3 Freaky Friday $1,601,871 +1% $65,127,050
4 Open Range $1,333,361 -0.2% $19,835,938
5 Pirates of the Caribbean $1,195,078 +3% $253,650,250
edited to add that Nemo passed the Lion King on the all-time chart today, making it the top grossing animated film (non-inflated).
http://www.boxofficemojo.com/alltime/domestic.htm