He is overrated. All others get dropped while he gets tauted as Barcelona's, best defender when in truth since Guardiola left and he lost protection of tiki taka, he has been exposed time and again. Just watch the champions league matches vs Juve in 2017- at fault for 2 of the goals, Roma in 2018- at faul for 2 if the goals (2018), Liverpool in 2019 - at fault for 1 of the goals.
Ronaldo has not had a good season despite being top scorer in serie A and is nowhere near the Ballondo'r based on his Juve performances regardless of how much you wish it to be true. Juventus are not going to win serie a for the first time after 9 seasons on top. He hasn't improved them at all.
If Barcelona win la liga, Messi can win it because in the second half of this season, his performances have been ballondo'r worthy of all players.
Lewandowski is tops scorer but in a 1 team league and does not have the profile to win the ballondo'r without winning the champions league/European cup.
In the end however, the champions league, Euro Cup and copa America will decide it. If, there is no stand out player in any of those tournaments (for champions league, it's mainly PSG having individuals), Messi wins it provided Barcelona with la liga.
To be fair there is no one in particular would win it for sure base on current standings, and you simply can’t ignore all the factors listed above. For example:
Lewandoski:
- 43 goals 6 assists in 37 games
- may win BL (currently 1st)
- Quarter final in CL with 5 goals
- top goalscorer in BL/top 5 league this season
Messi:
- 36 goals 11 assists in 44 games
- won domestic cup, currently 3rd in league (chance of winning double)
- Last 16 in CL with 5 goals
- will play in Copa (host country advantage)
- top performer/goalscorer in La Liga this season
Mbappe
- 37 goals 10 assists in 43 games
- currently 2nd in league and semi final in domestic cup (chance of winning double)
- semi final in CL with 8 goals
- will play in Euro (tournament favourites)
- top goalscorer in French league this season
Ronaldo:
- 34 goals 5 assists in 40 games
- may win domestic cup (in final)
- Last 16 in CL with 4 goals
- will play in Euro (defending champion)
- top goalscorer in Serie A this season
Haaland:
- 37 goals 7 assists in 38 games
- Quarter final in CL with 12 goals
- top goalscorer in CL this season
In fact any of the above would have a claim to win it, especially if any of them would go on and win Euro/Copa this summer. It isn’t really that hard, there’s one country winning Euro and one winning Copa anyway, if the top players happened to be in winning team. Let’s say France winning Euro and Mbappe scoring 3 goals, he will win it based on that fact that he is among top performer this season plus winning biggest Euro trophy, even if he only managed some decent contribution there.
In Messi case, no matter how brilliant he was since turn of year, if Barca didn’t win La Liga, he would end up in similar season as Ronaldo (similar stats, similar no. of trophies, similar CL progress, similar league standings etc), which then depends on how well they progress in Euro/Copa if they want to compete in Ballon D’or again.
And of course there is also outside chance for players like De Bruyne etc, if he helps Belgium winning Euros and City winning treble.
What if England win Euro, Kane may even have an outside chance there. He is top goalscorer/assist in PL, his output matches or even better than any top players in world this season, and assuming that he is also top goalscorer and champion in Euro, he may win it.
Kane:
- 31 goals 17 assist in 45 games
- top goalscorer/assist in PL this season
- (assumingly finished as top goalscorer and won Euro for England )
Don’t get me wrong, Messi has been brilliant this year and I think he is currently the best player, but on current standings, he didn’t clearly stand out among top 5-6 players listed above, especially with other big factors coming to play in summer.