I think you need to go back and look at Shaqs numbers from 2004 to 2006 and then again in 2008-2009. KG wasn't "Clearly" better than him at all.
2004: KG outperforms Shaq in I think every advanced stat there is in one of the most dominant individual seasons of the decade.
2005: I actually would have voted Shaq MVP that year over Nash, but KG still outperformed him as an individual in just about every advanced stat there is.
2006: KG again outperforms Shaq in every stat that there is, but by a wider margin.
2008: Ditto, by an absolutely huge margin, and this time KG also wins Defensive Player of the year as well.
2009: KG ended the season injured, and this was actually their closest season statistically in the last five years or so. But considering that their box score stats were somewhat comparable but KG was still arguably the best defensive player in the NBA before he went down, I still think KG outproduced him pretty solidly pre-injury.
2004- I will give you, an MVP season is an MVP season. But still, shaq's 22/11/ 2.5 blocks and 3 dimes is nothing to sneeze at. And as long as we're on the subject of Assts, I don't want a dominant low post scorer to have that many dimes, even if they are as talented a passer as Shaq is, I want them to score when they get the ball or to reset the offense. On the other hand, I do want my PF like KG who prefer to play outside the post to be able to make precision passes anywhere on the court. I think KG had a better season, but I don't think he FAR outstripped Shaq.
2005/2006- KG Out performed him because he had to, this will become important later on. When a superstar has no one around him its incumbent upon them to put up better numbers. Shaq's numbers went down after 2004 because by then Kobe had arrived and then he went to play with DWade and so he got less touches. Remarkably, Shaq lead the NBA those years in FG % while still getting 20/10, which to me shows that he adapted to getting less touches by becoming absurdly efficient. Proof is that after 2003 Shaq went from averaging 18 shots a game to averaging 14/13/14 and yet still averaging 20 ppg. KG: 20/17/16. Also, Shaq's rebounding numbers took a hit because he played next to Karl Malone in 2004 Who averaged 9 boards a game and the Udonis Haslem 9/8 per game. Better rebounding side players than KG ever had. Shaq's efficiency in his last year in LA and the first two in Miami are something to be applauded.
2008- Bad year for the big fella.
2009 - Shaq was having a better year than KG before KG got hurt. Its the first year that their rebounding numbers were close, probably because Shaq was playing with the hustle adverse Amar'e.
My point is when two guys are this evenly matched, championships become the final measurement.
Right, and it was a reasonable tiebreaker...in those years. Shaq beat KG by a relatively narrow margin in 2000, 2001, and 2002 in large part because he was able to lead his team to a title. For instance, in 2000 Shaq was the MVP and KG was 2nd in the MVP vote, but Shaq led his team to a title and KG's Wolves went out in the first round. I'm fine with that. Repeat that story in 2001 and 2002, that's fine. Shaq wins the first 3 years of this decade, but KG held his own. Both were top-5 players.
2003 - 2005, as you point out, Shaq was still playing at a very high level but KG was outplaying him. Call it a similar margin to Shaq's leads from 2000 - 2002, I'm fine with that. So by 2005 they've played each other pretty close to a standstill, but give Shaq the tiebreaker for the first 6 years of the decade because of the titles. I'm still ok with that.
But from 2006 - 2009, a period that makes up 40% of this decade, KG wins by a much larger margin than either enjoyed earlier in the decade. In 3 of those 4 years Shaq was hobbled for large parts of the year, and even when he played his production and impact were well below what KG was doing. The only year that was even close out of that group was 08-09, and I think KG was still definitely having a larger impact before he went down in '09 as well.
You mentioned at some point numbers vs team situation, but that's a big part of why I like looking at advanced stats more than just box score numbers. In 09 the Suns needed Shaq's box score stats more than the Celtics needed KG's, but in terms of differential (i.e. production vs opponent's production) or team impact (i.e. the +/- stats) KG had a very distinct advantage over Shaq in '09. And that was the year that was remotely competitive, whereas in 06, 07, and 08 KG just blew him out of the water.
So yes, if 2 guys are close and 1 has more titles maybe that is a reasonable tie-breaker. From 2000 - 2005, if that's the standard you want to apply to break the tie, I can't be mad at you. But once you add in those last 4 years where KG on the whole drastically outproduced Shaq, I no longer think the first condition holds. The titles are no longer the tie-breaker for the whole decade, they instead are the only thing that keeps the decade-long competition close. In my opinion.