Let me help out here...it was
20 for 27 for 74% in 2005.
2001 was Longwell's worst year, 20 for 31 for 65%, including 7 for 14 from 40-49 yards.
In his other 7 seasons with the Pack, his yearly averages ranged from 80 - 89%.
His two best years were with the Vikes...93% and 94%.
Longwell's 82% for his career with the Pack was quite good for an outdoor kicker. He was 86% with the Vikes. That 4% difference sounds like a good rule-of-thumb-adjustment for outdoor vs. indoor comparisons.
http://www.pro-football-reference.com/players/L/longwrya01.htm
I wouldn't call any of Crosby's seasons outstanding except for last year, his only season over 80%. 2007 and 2008 were decent at 79+. I'd say he's been on balance, over 6 seasons, about an average outdoor kicker at 78%...maybe a bit better than average excluding this season.
Longwell, on balance, was the better kicker, especially if you put aside that 40-49 slump in 2001.
http://www.pro-football-reference.com/players/C/CrosMa20.htm
On the general issue of FG %, I'd look at the stats for 31-49 yards to gauge general effectiveness.
Even the worst kickers make nearly everything from 30 on in (the league is 160 out of 161 this season from that range). Some kickers get more chip shots to pad their %. From 50 on out, stats get distorted as well...kickers without big legs are not asked to try the long ones as often (fewer misses raising overall %), whereas kickers with big legs are asked to kick the long ones more often (more misses dropping overall %).
Further, regarding long kicks, even the best kickers with extended resumes...guys like Akers, Vinatieri, Janakowski...are at about 50% from 50+. Which raises the question of the wisdom of even trying those kicks unless the clock is running down, especially if you have a decent punter or short yardage to go.
31 - 49 is where you expect your kicker to earn his pay.