I have them at the same level. Ultimately, it comes down to this: How often did someone get Forsberg off his game the way Detroit (2009), Montreal (2010), Philadelphia (2012), and Boston (2013) did to Crosby? Maybe Chicago in 1996? The guy danced around Lidstrom and Chelios in years where they were healthy and Sakic wasn't contributing. Crosby's incredible, but he couldn't break-through against an injured Detroit team, so I don't know that he'd fare any better against a pre-Salary Cap one when he's getting handled on a yearly basis.
Forsberg:
-1 goal 1 assists in 6 games against Chicago in 1995-1996.
-2 goals 2 assists in 6 games against
Detroit in 1995-1996.
-0 goals 1 assists in 5 games against
Detroit in 1996-1997.
-2 goals 3 assists in 7 games against Dallas in 1990-2000.
-1 goal 2 assists in 6 games against San Jose in 2003-2004.
-2 goals 2 assists in 5 games against San Jose in 2006-2007.
-1 goal 4 assists in 7 games against Minnesota and
Detroit in 2007-2008.
----------------------------------------------------------------
GP G A P PPG
42 9 15 24 0.57
Compared to those series you mentioned for Crosby:
-0 goals 0 assists in 4 games against Boston in 2012-2013.
-3 goals 5 assists in 6 games against Philadelphia in 2011-2012.
-1 goal 4 assists in 7 games against Montreal in 2009-2010.
-1 goal 2 assists in 7 games against Detroit in 2008-2009.
----------------------------------------------------------------
GP G A P PPG
24 5 11 16
0.667
So taking Crosby's series you listed and the worst ones by Forsberg statistically, Crosby still wins. Remove the Philly series (not sure why you included that one, he played fine), Crosby has in his 3 worst series:
Crosby:
GP G A P PPG
18 2 6 8
0.444
Still not much worse than the Forsberg ones above. Of course if you take only Forsbergs 3 worst you get:
Forsberg:
GP G A P PPG
17 2 4 6 0.352
In points Crosby is better at his worst than Forsberg at his worst and better at his best than Forsberg at his best. Forsberg's best series is 12 points in 7 games or 11 points in 6 games. Crosby's is 14 points in 6 games or 13 points in 7 games.