The valentines at Rite Aid and Walgreens tend to fall into the general categories of "gross," "unfunny," or "taking far too seriously the amount of sentiment one can pack into a $2.79 purchase."
Five minutes in PhotoShop and you can do so much better for your Valentine. I got the image here from art-e-zine, and they have loads more that are neat-o.
Yet, the librarian in me had to press onward. You'd be amazed how many libraries have their greeting card collections digitalized. You can find valentines from days of yore here, here, and here. And you can see some pretty creepy ones here.
Dear readers, I lurve you all. I'd say I choo choo choose you, but probably everyone is telling you that.