I like that question!
If I go back and see my first pictures, the ones now are seriously better, but I think that has something to do with general photographic knowledge, not the gear to an absoulte.
That being said I would without ANY doubt say , because it's a fact, that most of my pictures today couldn't have been done with anything else. How do I know that? I have bought new gear because the old didn't do it right. I've been through; 350d, 400d, 1d3+5d1, 1d4, 5d2, 5d3 and now the 1d X and I must say, the 1d X takes it all to a different level. In the short time I've had it I've gotten more funny and unseen moments, (in my pictures) than the others put together. That blows my mind.
But as we all know, that is only the body. I have no idea how many lenses I have owned, sold, traded over the years, but it is around 35-40, and my current setup is the only set of lenses that have kept up with the 1-series advantages imo. And although I can sure as hell take a good picture of my daughter (9 months) sitting on the floor with pretty much anything, but to do it at the superclean 1600 iso with the 1d X and have the 85 L II (that now has fast enough AF) makes that image something more than a snapshot, it's now a keeper, and a fun memory due to the burst of 6 images (at 12 fps) I had one with a funny expression. It's the little things.
And then I can go out, shoot a surfing contest and come home with all tack sharp images and can pick the precise moments.
For me there has been a significant step up for each lens and body, and a BIG step when combining them.
But what has made the most impact on my images is actually something else. It's a book called "Light, Science & Magic" and the "Lightning 101" over at www.strobist.com
. It's when I went with wireless lights I really starting to have fun and get images like the one I saw on the "internets" and got a whole other undestanding for what it takes to make a great image.
And you'll also get a more and more trained eye and that combined with knowledge makes it very annoying (for me at least) to use gear you know could be better. If you get the images you want with what you have, that saves a lot of money.
It's when you buy your first L-lens it all goes out the window