I believe neither of them is currently the best haha. I mean they were the best for 10 or more years, but right now there are better players than them such as Mbappe and Haaland, which in my opinion are going to be the new main rivalry just like Messi vs CR7 so far.

However, to answer your question, it isn't easy to say. Messi won more individual and collective trophies but CR7 won collective trophies of better quality. CR7 won 5 Champions League with 2 different teams and with him as the main star, while Messi won 4 Champions League with only 3 of them as the main star. In his first Champions League he was just a teen on the bench.

So we have CR7 obtaining the ultimate victory in the Champions League as the star of this team 5 times, while Messi only did this 3 times. Also, CR7 has been successful in different clubs and countries, while Messi has only been successful in one team where he has played since he was a kid, which makes thing easier for him.

CR7 also won the UEFA Euro in 2016 while Messi hasn't won any Copa America so far.

The argument in favor of Messi is easy, he has won more individual and collective trophies while also being around 2 years younger than CR7.

Personally, I prefer CR7 but any choice is good. However, as I mentioned at the beginning, the new super stars in football are Haaland and Mbappe. Messi and CR7 are close to retirement now.