Only real letdown was 2010, IMHO, I think we were better than Pitt and GB and could have won it (easily). 2012 to a certain extent but injuries decimated us before and during the Ravens game. 2013 was a long shot, 2015 was marked by numerous injuries in the second half of the season and lots of guys were well below 100% heading into AFCCG. 2009 was underwhelming, 2006 the receiving corps simply was not up to the task, 2005... another season marred by injuries all over the roster. So, yeah, I believe we could have had one or two more under the belt, but then again, GB had only one trophy in last 20 years with 2 HOF QBs.
From 2005-2013, it definitely felt like we left ring(s) on the table.
Overall though:
2001-We were a team of destiny IMO but I honestly think the Rams were the best overall team that year
2003-Best team.
2004-Best team.
2006-Overachieved with a weak WR group and even then, we blew a lead to IND where the winner was gona beat the Bears.
2007-No words need to be said.
2008-The big injury.
2009-Not good enough.
2010-Ahead of schedule in a "rebuilding" year but in a year with no dominant teams, we didn't take advantage and probably had our worse upset since it was to the Mark Sanchez-led NYJ in the Divisional round no less.
2011-In a year with 2 teams (GB, NO) who had a better statistical offense than us, we fell just short in a very winnable game for SB 46. Not sure if we were the best team all year where the competition was better overall than 2010.
2012-Injuries.
2013-Injuries.
2014-I thought we were the slightly better team than SEA. It was a strong year in the league overall.
2015-Injuries.
2016-I thought we were the best team all year.
5 rings (and counting) in 7 SB appearances for the current era thus far is a fair result IMO. The only year where I felt we were CLEARLY the best team and didn't win was obviously 2007.
If the NFL playoffs were a best of 7 series, we could be looking at as many as 5-10 rings as we were good enough to win it all in 2001, 2003, 2004, 2006, 2007, 2010, 2011, 2014, 2015, and 2016.