Replacing 3 rides with 3 rides keeps the ride count the same, or replacing 3 rides with one ride that has a massive queue... doesn't matter. Its all about making the ride count go up... the more rides there are, the longer the people will stay in the park, the longer they stay in the park, the more money people will spend. "ITS THE CIRCLE OF LIFE... AND IT MOVES US ALL..."
While the park needs more big rides, it also needs the small flat rides to balance it out. You can't expect people to just waste their time in line for one big ride like SeaRider when they can do a lot more in the park.