You don't use "secondly likely", instead you use "second most likely".
You may also use "most likely, less likely, and even less likely" for that, but I can't imagine a situation where you want to say this in front of the very girls you're categorizing, they might end up changing that sentence to "most likely got slapped by"
The above paragraph was written (typed?) before the question was edited.
There are other ways to express ascending/descending priority such as this case. For example:
- "If I have to choose, I'd take the left one, if that's not available I'd take the middle, if that's not available too I'd take the right one"
- "To me the left painting is the best, middle painting the second best, right painting the third"
- "I prefer left painting over the other paintings, and I prefer the middle painting over the right one"
If you insist on using "most likely", then you can either use descending or ascending style:
- "most likely, second most likely, third most likely" - descending
- "most likely, less likely, even less likely" - descending
- "likely, more likely, most likely" - ascending
- "likely, more likely, even more likely" - ascending