The 60D, the T2i/550D and the Canon 7D all use the same sensor. It is a 1.6x crop factor sensor that produces 18MP pictures. In comparison, the Canon 5D Mark Ill uses a 1.0x full frame sensor. The larger full frame sensors are able to collect more light than smaller
sensors.
ISO performance just keeps getting better and better with each new generation of camera.
I've used ISO 6400 with my Canon 60D and had no big complaints. I made the cover of a magazine with a picture shot at ISO 6400 with a JPEG.
The Canon 5D Mark I| will run circles around the Canon 60D with regard to ISO performance. But that is not a fair comparison since the Canon 5D is a full frame camera and costs more than twice as much.