We should wait and see how the CL games will go through.
Ronaldo has "the luck" to be in a more competitive group, I mean - the whole world will watch the RM - City games or even RM - Dortmund. A big performance in those games would be a huge boost for the Ballon d'Or, while Messi won't have such a chance against the teams we picked. I mean, he could still score 3 against Celtic, but it would not leave such an impression as massive performance from Ronaldo against the champion of England for example.
The CL draw made Ronaldo a big favor, so it's up to him to take advantage of it. He's got the big scene needed to convince, especially when we're talking about those two games with City.