In my kitchen, I use subway tile to make a backsplash (well, I went up about 2 feet). Anyway, the seal between the counter and the tiles keeps cracking! I have tried 3 times. I am about to try again... Any tips, or some special product that will help it not crack?

How big is the gap?

What did you use?

I used the standard kitchen & bath caulk. The gap is maybe 1/8 - 1/4 "

The 1/4" gap is the problem. Caulks are generally not designed to handle this.

You're going to have to provide a backing with say one of the expanding foam adhesives, so that you have a max of about 1/8 x 1/4" area to fill.

I might try this or similar. Sil-Bond RTV 3500

Try a marine store.

I will double check the height of the gap.. (just going by memory lol... )

So basically, I need to fill in the "back" of the gap with something else, then cover the front with some good caulk?

Yep. Something like this:

Latex Foam Sealant