These rosters are not even close to being similar. You have a veteran corp group on both sides of the ball. A veteran QB, throwing to arguably the best WR of the last decade (with all due respect to C. Johnson over the past 3 years), who was tutored under the likes of an Anquan Boldin his few few years in the league. Now you add a talent like Michael Floyd as a compliment, and you have a dual threat at WR.
A defense who has one of, if not the most dynamic player (sorry Richard Sherman but I will take Patrick Peterson over any DB/CB in football) and now line him up across from Cromartie, to go along with Ty Mathieu in what makes up a pretty good secondary. Maybe even better than Seattle. The d-line is not slouch, Calais Campbell looks like an All-Pro whenever we play him.
Did I think they would be this good? No. have they lost some key players due to injury/suspension. Oh yeah. But it shows the depth of their overall roster that they can plug in veteran guys rather than the like of rookie and second year players. They acquire a Ted Ginn as a 4th WR, and return guy, we add a ROOKIE. They add a Larry Foote to step in as a replacement at LB, we add Will Herring.
I understand, and have a harder time coping with their success than say the Colts, as we have touched on. But again, these are teams that are so much further along in the development of their roster than the Rams were. But, I also understand, at some point, they need to get the 2nd and 3rd year players to step up and start being contributing members, or once again, they end up chasing their tail all over again, and continue to replace them with even younger players.