Well he's far, far more consistent that's for sure. Murray, like Djokovic and Nadal made use of his talent early on in his career. Started reaching his top level at a young age. Stan's had a very unique career trajectory. He always had an aesthetically pleasing game, but always crumbled under pressure. He had the odd good tournament here and there, but never anything more. The coach change a few years back to Magnus Norman really helped him get over the mental hurdles of constantly bottling it vs the 'big 4'.
On winning grand slams - I definitely disagree there. I have huge admiration for all the top players, with Nadal and Murray being my favorites, so it bugs me to see him lose, but Murray's never had the game to compete with a Djokovic/Nadal/ Federer who are having a good day. He's always been 3rd or 4th best. Don't get me wrong, he definitely deserved the 2 grand slams he has, he played very well, but given the competition, its about right. IMO Wawrinka, if he'd had the right coach and a better mentality when he was younger, would have been a big menace for the big 4 even in the Fed, Nadal and Djoko heyday of 05-14. In the key matches, while Murray often comes up short (I just don't think he has the weapons to hurt the other guys at the top, who tend to be his opponents in the finals), while Stan on a good day has that in his locker.
Of course, Murray has been unlucky in that when he was coming through he had two of the best players of all time to get past (Federer and Nadal), then when Nadal starts to fade he has to deal with Djokovic. Obviously those three were always likely to win more titles than him, but I feel that on a few occasions he's beaten himself as much as anything - I remember a couple of big matches against Djokovic where he was ahead and playing well, he made one mistake and let it get to him, went to pieces and lost. He seems to do that less now, but as someone said earlier, he still seems to be too conservative at times - just plays his normal game, which is good, but not quite good enough. He did play some brilliant shots at times yesterday and showed tremendous mental toughness in that long game, but it was always reactive, trying to resist Federer and hold on to his serve, rather than trying to dominate him and put him under pressure. Easier said than done obviously, but if you just defend and let him play, you've got no chance.
However in some ways he's been a victim of his own success and consistency - if he'd only got to 3/4 finals and won 2 of them, we'd all be saying he'd done as well as he could have - but the fact that he's got to 8 finals (and many other semis) yet only won 2, leads you to think that he could've done better given his ability. I think everyone takes for granted now how good he is - when you compare him to Tim Henman, who was good but only ever flirted with being a top player, Murray is on a completely different level.
In some ways he's a more interesting player than Federer and Djokovic, because you never quite know what you're going to get - when it comes to the big matches he often gives the impression that he's battling against some demon or other, against his own lack of belief in himself. He is mentally very tough but it's a different kind of toughness to Federer and Djokovic. Murray will keep fighting and can come back from seemingly impossible positions, but at times his confidence seems brittle - if he makes a big mistake he often lets it get to him and it affects his game, whereas those two seem much more controlled and able to shrug things off.
I really like him, I just feel it's shame he hasn't won more titles when he has the ability to do it.