My ranking...
1. Bush
2. Christie
3. Paul
4. Cruz
5. Perry
I voted for Cruz since I think he's undervalued on this forum. Read blogs like Redstate. Cruz is the darling among a lot of conservatives. Walker is really just a consensus candidate that isn't unacceptable to anyone...but he's SO BORING. But there are way too many charismatic candidates or candidates with strong niches (i.e. Paul with libertarians or Bush and Christie with moderates) for a consensus candidate to cut through the field.
Don't make the mistake of assuming "blogs like Redstate" mean anything. Republicans on the internet absolutely despised McCain and Romney in 2008/2012, and they still won anyway. Hell, Free Republic actually
banned Romney supporters because they were "communist liberals" or something. That said, you may have a point he may be somewhat undervalued, simply because the field is so large it could only take a strong debate performance to propel him into a win in Iowa or South Carolina. And with a larger field, his small but loyal base is more powerful than it otherwise would be.