Speaking on Sky Italia, Paolo Di Canio said: "I prefer a human with a soul than an alien with no emotions. I prefer Cristiano Ronaldo.
"Lionel Messi has shown the limitations of his personality. Booing him is justified. Thousands of fans were waiting for him, dreaming of him, but his behavior has not been correct.
"Neymar is even worse. He hasn't been doing anything special and last month he said he wanted to go to MLS for a three month vacation. I mean, have respect, there must be a problem."
Messi and Neymar failed to make an impact as Paris Saint-Germain crashed out of the Champions League with a Round of 16 defeat against Real Madrid.
The former Barcelona duo were booed by PSG supporters last week and it remains to be seen whether they will remain at the club beyond the summer.
