Ah, I love Stereo Love.
That's older than you think, it's bordering on two years old now!
(actually, might have got bigger in America later, the Romanian hits tend to, so ignore that)
I think that's the first thing I noticed about On The Floor when I first heard it tbh, so that's quite accurate. That riff is lovely. I don't think it directly samples Stereo Love but they're along the same lines.
On The Floor's been quite a trendsetter, a lot of female pop tracks have been rather similar to it since. I'd forgotten about the Stereo Love connection until now.
Here are two of the most blatant examples (and the two I was principally thinking of):
Fairly generic but I do shamefully like it, it's almost a complete pastiche of On The Floor.
And this (I will use any chance I get to show this off):
From Charlotte Perelli's new album (Eurovision winner in 1999 and returned in 2008) featuring Kate Ryan (ESC Belgium 2006), the riff sounds VERY similar to On The Floor, and it's quite a wonderful pop track.