The American Falls at Niagara in 2005
The Niagara Falls are certainly magnificent. It's a matter of personal opinion certainly, but I found Burney Falls to be more intricate and beautiful to behold. It's in a much more natural setting and isn't as commercialized. I saw both in peak season, but Burney Falls was certainly less visited. Though we passed a few other people, we pretty much had the place to ourselves and you could watch the falls in solitude. My experience at Niagara was that it there were more distractions around the falls.
The viewing angles of Burney Falls were also a bit better. Owing to the large amount of water coming over Niagara, the mist, while fun, prevented you from seeing the falls well up close.
I did not take the time to see the falls by boat, which did seem like it would be interesting, but I thought the most fun (and free) viewing angle was from the top of the falls watching the water tumble over the precipice.
So, Niagara Falls still gets 9.7 stars on the Nate's Nonsense Waterfall Rating Scale, which is remarkably high, but slightly lower than the 9.9 rating for Burney Falls.
And I know you are all having a difficult time putting the height of the falls in perspective, so I've added Niagara Falls to the handy info graphic below: