It's typical question for an average football fan but an easy one for those who can understand football.
So I will write in an average football fan view
Let's see everything one by one
GOALS
We all know both are good at scoring goals.
Winner: Both
Messi has more number of assists than Ronaldo every year because he plays like play maker more than the finisher.
Passing:
Messi passing capability is better than anyone in the world.
Free kicks:
Ronaldo scored more free kicks (46) than Messi (31) but Ronaldo's conversion rate(4) is half of Messi conversion rate(8).
Ronaldo free kicks
2015/16:3(including country and club)
2016/17:0
Messi free kicks
2015/16:10(including County and club)
2016/17:3*
Ronaldo has much better conversion rate also scored more penalties than Messi
Dribbling:
Who can dribble like Messi??
Ronaldo has good dribbles while he is in man united but not good enough because Messi is much better
Physic:
Ronaldo has much better physic and can win the ball in the air
Consistency:
5 balloon d'ors
10 consecutive years in world top 3
Scored in 21 consecutive la liga games
Team play:
Ronaldo inspired his team Portugal to win Euro cup but when it come to Real Madrid story is different he is often criticized for going for glory himself rather than passing the ball.
When it come to Messi he is well known for his great team work and unselfish play
Discipline:
While Messi has one red card in his entire career.
Ronaldo has 8 red cards in his career know for aggressiveness.
Trophies:
Team trophies
Overall:
Ronaldo good in shooting, penalties, physic
Messi good in everything else like dribbling, passing, team play, patience, discipline etc.
Ronaldo know how to speak English while Messi knows how to play football.
^^