The disk image created by Win 7 is not the same as that created by Ghost in that the two images would not be identical bit-for-bit. However, when images are restored by their respective programs the end result would be the same, a fully restored disk.
As far as I know, Win 7 is the 1st MS OS to include disk imaging but I'm not 100% certain of that.
There will always be a need for 3rd party apps because they have different features or they're faster, better interface, more intuitive, etc...
One free imaging program that gets recommended a lot on these forums is Macrium Reflect
. I've never used it but I understand it's pretty decent.