1-If there was one result in tennis you'd change in history (since you started watching it) what would it be?
2-Who's the better player, Moutinho or Veloso?
3-If Benfica played Real Madrid in the CL final who would you root for?
4-Rivaldo or Ronaldinho?
1-Tough to say, unfortunately my favorite players have lost a lot of close big matches over the years I wish they had won. For Safin, I'd highlight USO 2006 vs Haas and of course AO final in 2002. But the match where I did wish I could change the outcome if I could was not that close, AO 2004 final, the title would have suited him better that year than in 2005 after such an extraordinary run. For Ancic, there's that infamous Hamburg match against Boredo and maybe also the Wimbledon semis against Roddick (although odds are he'd have lost to Federer in the final). For Del Potro, RG 2009 semis and Olympics 2012 vs Federer and DC final against Nadal. Also wish Tsonga and Berdych had won their Slam finals, but I like Nole too and Berdych never had a shot vs Rafa to begin with so... Cilic's losses to Murray in AO 2010 and USO 2012 were pretty frustrating too, as well as Tsonga's heartbreaking loss to Nole this year at RG. And I'm sure there's more...
It's hard to pick just one overall, but if forced to do so I'd maybe go with the Wimbledon 2004 semis. I'd have loved to see Ancic get a chance to play a Slam final before injury and illness terminated his career. All the other guys I mentioned either had great careers and won a Slam or still have time to do so.
2-Moutinho is better, I think. He's Portugal answer to Xavi, nowhere near as good of course.
3-Another very tough question. I'd most certainly not be watching that match; Benfica though, I have good friends who support Benfica and almost all my family does too - their reaction might be unbearable at first but I'd be happy for them. Besides, can't let Real get La Decima.
4-Rivaldo. But I'm extremely biased here, he's my favorite ever player and my hero growing up.
Who is more talented, Safin or Nalbandian? IMO, it's Nalby by a hair but Safin obviously had greater weapons.
Safin for me, but they are both very talented and it's very close. As you said, Safin had greater weapons; amazing serve (while Nalby's has always been a liability), better FH, much more power off the ground. Nalby has a better return (although Safin's was pretty good too), better overall touch and use of angles, and his movement seems more natural, almost like Federer's.
It is very close for sure, I just feel that Safin at his full potential is that extra bit harder to stop than Nalby.