It's a very subjective opinion to state "no he's...", so here's mine.
Nowhere near among the best in history since he never had an aura of excitement, mostly due to lack of technique and vision where I find him quite average.
Ronaldo was always a great football project, starting from his training, game recoveries, sacrifices, determination and especially - marketing.
I don't even consider him to be among the best 10 players, since I admire Iniesta's abilities far more then his, not to forget players like Zindane, Xavi, original Ronaldo, Ronaldhino, or even E.Cantona, older stars like Pele, Cruyff, Di Stefano, Beckenbauer, G.Best, Maradona, etc. It's too crowded with raw talents to consider him even even close to Messi.
Messi is top 3 easily in my head. Not because I'm Barca fan, but because I haven't seen a better player who is so technical, consistent and efficient. I have not...and I can hardly imagine a better player. I just don't see space for that. Maybe if he was better defender or had better stamina to run like crazy for 90 minutes...
I haven't seen Maradona or Pele, but since these two are often put at the top, I will respect that and put Lio right beside them. Messi is epic talent. Ronaldo is just nowhere near that.