As far as primaries go, Cruz kinda needs Trump in the race to make him seem at least a little bit moderate. I think a Rubio v Cruz head to head would be pretty one sided.
For the general election, Trump would give the WH to the Dems, Cruz would be in a battle, and Rubio would win easily. I'm still holding out hope that a strong NH gets Kasich in the mix but it looks like Rubio will be the establishment/moderate torchbearer.