Federer faces a lot of the same "problems" (in the eyes of neutrals) that Messi does in CL in football in terms of legacy assessment.
Federer was the one who set the benchmark and pushed the level of GS play to new heights. Messi did the same from 2008-2015 with not only trophies but overall dominant performances (goals + assists, 10+ dribbles in CL matches lol).
Nadal and Djokovic with their later peaks had the advantage of gunning for Fed's benchmark and both have now surpassed him in "winning" in GS/Masters. Same with CR7 after Messi had set the bar with 2 trebles and CL masterclasses by 2015...and then CR7 ended up with more CL wins than Messi. Call it the curse of setting the benchmark. I'm sure had peak Barca/Messi known that what they were doing between 2008 and 2015 in CL would be surpassed (in wins) by 2014-2018 RM, they would have pushed an extra gear in CL. But in 2015, 3 CL wins in 7 years was considered an amazing dynasty in modern football. For reference, the all time great Milan had also won 3 CLs in 7 years in the 80s and 90s.
The amount of wins is definitely a factor for the title of "greatest", but things like absolute peak level should also be considered more. I would back prime Roger very evenly against prime Nadal and prime Djoker and he probably is better than both (Roger's forehand between 04 and 07 on fast courts was another level).
Thankfully, Messi has a lot of other major accolades (10 LL, Copa, 7 Ballon, 6 golden boot etc.) that help him be > CR7 trophy wise in the eyes of most neutrals despite being behind in CL wins.