My take on the Ronaldo vs. Messi debate:
In recent times, I think Portugal and Real Madrid adapted their game for Ronaldo's benefit, while it was the opposite with Messi with Argentina and Barcelona.
Ronaldo was slowly losing pace so he moved to play more up front with less dribbling and less participation in buildup, which resulted in many clutch goals for him. Real Madrid also kept quite a steady lineup in the past few years. They have great attacking fullbacks, complete midfield with 3 very different players plus a varied set of wingers to support him.
Whereas Barcelona lost Dani Alves, Xavi, Pedro, Neymar, now Iniesta who combined with Messi enough so that he didn't have to do everything himself. Now he's the main creative outlet and their biggest goalscoring threat (with Suarez declining fast), so opposing teams just triple defend him which ultimately seals the fate for the whole team. Might turn out better for Barca now that they have Coutinho (who didn't play CL with them, hence the elimination) and with Dembele not getting injured all the time. Argentina is far worse considering they have a shittier defence and a shittier midfield and can't fit all their strikers into one formation.
Player vs player - Ronaldo is better at penalties and headers, Messi at dribbling and scoring from midfield, both are pretty clutch in the box though.