Aries and Cancer are very different in personality and in their needs and essentially what they want to get in life, and that is what they want to get in relationships.
Aries looks for something grand, something adventurous, and likes to be the first to try out, explore, try new things. It doesn't necessarily mean new sexual positions, although that as well, but generally is an explorer in life. Cancer is more home-oriented, not necessarily house-oriented, but home in the sense of making a nest, making something secure, of giving and receiving nurturing, of creating something very stable and safe.
So these energies are rather opposite to each other, and they would have to work out the temperamental differences. Immediately in this relationship, there is a lot of sensuality. Both of them are greatly affectionate and certainly enjoy and derive enormous satisfaction from the feeling of blending and melding sexually.
But the temperamental differences very shortly are going to raise their ugly heads in this relationship. Cancer will feel overwhelmed by the Aries bossiness, by the Aries need to get out, to experience, to have new friends, to do this, to do that. Whereas Cancer really wants to have a mated relationship.
I would say that they can work it out, but it would take a lot of patience, and it would take a lot of time.