If the Ballon d'Or is intended to recognise the best footballer then it will go to Messi, as Messi was the best footballer in the world last season, is the best footballer in the world this season, and will be the best footballer in the world next season. And his performances across the season as a whole were simply far better than anyone else. Literally on a different plane.
If the Ballon d'Or is to just be awarded to a player from a team that won the Champions League then give it to anyone. It's not a measure of the best footballer anyway. You might as well give it to Nacho. I mean, he won the Champions League, so he must be better than Messi.
I personally do not understand why such awards now have to go to players who won trophies. That is what team trophies are for. Individual trophies are for individual performances, and Messi has been comfortably the best player in European football for season after season.
The fact that Ronaldo may after this year have won more Ballon d'Or titles than Messi is literally a travesty. The implication from this is that Ronaldo is the better player, whereas everyone who remotely understand football and is remotely objective knows that Messi is clearly the superior footballer, great player though Ronaldo is and has been.
In terms of who wins it out of Modric and Ronaldo...Modric isn't fit to lace Messi's boots, and Messi is significantly better than Ronaldo, so who cares who wins it out of the two of them?