Whether it's injuries or inconsistency, something has put him clearly below Crosby in current ratings and kept him from reaching #1 depending on the criteria set out by the OP. Again, after 2008 Malkin would not have been on the #1 tier because his peak at that time was not as good as Crosby's or OV's, both of whom had better rookie campaigns and Crosby had the better playoff resume. After 2009, he definitely was but since it was only for one year, I think it's reasonable that he doesn't get the #1 rating.
The "what if" scenario for both players doesn't change that IMO. Crosby likely gets the 2 or 3 more Art Rosses and puts up at least one peak season that would have been best of the era.
Even moreso, Malkin is still #3 after 2009 and Crosby has entrenched himself since 2011 as the clear #1.
But this is a big "what if". I'm not sure Malkin can get thru a season without something affecting his PPG. According to you, he only has one "healthy" season since 2009. Yes, Crosby gets injured but mainly it has not affected his PPG save for maybe the wrist injury at the end of last year.
Prior to his wrist injury, the injuries he had were not the type he could play through as you and others have touched upon. This means that he had time to rest and heal those injuries, not playing through them allowed him to maintain his PPG.
This is what Forsberg benefited from between 2002 and 2004. He had the best playoff of his career after sitting out an entire season and then followed it up with his best PPG season (since 1995-96) in 2003-04. He would then again get a PPG of 1.41 in 2003-04 as well but only played in 39 games. Do you think this was a coincidence?
A lot is talked about how Lemieux scored 76 Pts in 43 games in 2000-01. One, he wasn't even that old, he was 35 years old and two, he sat out for a whole 3 years and gave his body time to heal and rest. He also started the season at the end of December, so for those 43 games he played, his adrenaline was at a high, he didn't have to play long stretches and well he was in better shape health wise than he had been in 5 years. It also didn't hurt that he was a lot healthier than his own teammates and competitors who had already played about 35-38 games prior to Lemieux' comeback and most likely would have been dealing with minor injuries, fatigue, something that gave Lemieux the edge.
The only time Malkin had the novelty of resting somewhat over the past 4 years was right before his 2011-12 season. Again, do you think it was a coincidence that Malkin turned in his best season as a professional after having time to rest and heal his knee?
Another example of this would be Selanne, he pretty much looked done before the lockout. When the lockout occurred, instead of playing overseas like a lot of the other stars did (Lecavalier, Thornton, Jagr, Datsyuk, Kovalchuk), he decided to rest his knee. When the NHL started again, he turned in his best 2 seasons back-to-back since 1998-99. Again, do you think it was just a coincidence that his best seasons in a long time occurred after resting?
Crosby did look like he was going to have his best season in the NHL in 2010-11 before he got injured and that injury did occur at an inopportune time unfortunately. We will never know how well he would have played down the stretch. However the long rest (a whole calender year) allowed him not only to heal his head or misdiagnosed neck injury but also allowed him to heal and rest any other lingering injuries he might have had including the high ankle sprain. It's no coincidence that his best PPG as a professional occurred in 2011-12 and to add to this, he only played in 22 games so there was barely any time to witness a drop in his game, he was playing on all out adrenaline and full bill of health. Even then, that season, I remember even seeing it from Penguins fans themselves saying how Crosby did not look as dominant that season as he did in 2010-11 but still he had his points and high PPG right?
Then we have the 2012-13 lockout season. While many stars flew overseas to hone their skills in the KHL, the Swedish and Finnish Elite leagues as well as the Czech Extraligue, Crosby stayed at home and practiced and trained with a few of his teammates (Kunitz namely) and rested up and stayed fresh.
The NHL started again and while Malkin struggled with lingering injuries that he carried over with him from the KHL, Crosby on a clean bill of health caught fire right away. Not to mention that Kunitz, the player he had been playing and practicing with during the lockout, a player who also rested like Crosby, had his best per game basis season of his career. Again are these coincidences?
For the first time in a long time, Crosby played through an injury and lasted a whole season and while on the surface it looks like a dominant season since he won the Art Ross by 17 Pts, his own personal play suffered from previous seasons as his PPG of 1.30 for the season was the lowest of his career since his rookie season. It also didn't hurt that his most direct competitors and most obvious threat to him winning the Art Ross were injured and missed significant time; Stamkos, Tavares and Malkin all missed significant time. Giroux did also outscore Crosby by a significant amount in the second half of the season.
Context is important. It's not as simple as saying, Crosby got hurt but still maintained his PPG. There is a big difference between playing through injuries (Crosby did in 2013-13 so I'll give him credit for that) or resting and giving time for the body to heal itself.
The biggest test of Crosby's career will be in 2014-15, this season will make or break his legacy and current status as the best player in the world. Although Tavares and Stamkos never actually even scored 100 Pts, they are still young and have a lot of potential and clearly the skillset is there, whether they have done before or not is irrelevant, they are still a legitimate threat to Crosby for leading the league in scoring. Malkin, when healthy can never been counted out either. Will Crosby remain healthy and peak? Will he remain healthy but continue to plateau? Will he get injured, have a good PPG? Will he play through the whole season and regress?
We shall wait and see. Calling this the most important season of Crosby's career is a huge understatement.