The Texans have slowly gotten better, but no they wouldn't have beaten out the Peyton Manning teams on a regular basis. They are still not up to that kind of caliber.
I wouldn't necessarily call the Texans a perennial second best team. In all actuality they were the perennial worst team in the AFC South. The Titans were usually the second best team.
Only recently after Peyton went out injured did the Texans finally take control of the AFC South. But you also need to remember what all happened to the AFC South during that time period of 2011. Peyton Manning was out injured all season for the Colts and they placed dead last in the NFL. The Titans dropped Vince Young and fired Jeff Fisher. And the Jags got rid of David Garrard and fired Jack Del Rio.
Essentially in one year the entire AFC South except for the Texans totally imploded and started over. So the Texans were left to rule the roost.
As far as the Texans beating Peyton Manning and the Broncos, I think that was more due to good timing for the Texans. At the beginning of the season, Peyton was still recovering from his injuries. And he was still developing cohesion with his receivers. They hadn't learned Peyton's system and how to run the routes to perfection yet. Once they did, Peyton ran off the longest winning streak in the NFL last year.
The Texans won three impressive games last year, but an asterisk could be put near all of them. The first was against Denver, but Peyton was only 1-1 and like a side still getting things together. The second was against the Ravens. This may seem an impressive win until you look at how the Ravens were doing on the road. They lost to Philly on the road and Philly was horrible. And they nearly lost to the Chiefs on the road, barely scoring any points against another of the weakest teams in the NFL. Luckily the Texans played them in Houston, not Baltimore or the outcome could have been quite different. And don't forget the Ravens still had horrible Cam Cameron as offensive coordinator. Lastly, was the Bears. But the Bears unlike the past were winning off of their offense and Cutler's passing. They couldn't do that with the horrible weather that game in Chicago. While it was a good game, Houston got lucky a 3rd time.
I think the true marker of how good or bad the Texans and Colts are can be marked against the Patriots and against each other.
Neither the Texans or Colts reached elite status last year. The Patriots were able to easily beat both teams. The 3 elite teams last year were the Patriots, Broncos and Ravens. And you might be thinking, "But the Texans beat 2 of those three teams!" Yes, but the Broncos weren't elite until the end of the season. And the Ravens were elite at home. And the Patriots were elite all season.
I think the 2 year reign of the AFC South by the Texans ends this year. And it only gets tougher afterwards. The AFC South is rebuilding. In just 1 season, the Colts went from 2-14 to 11-5 and nearly took the AFC South title. And in the last game of the season, they controlled and beat the Texans, costing them the #1 seed. The Texans needed to win that game and the Colts didn't need to. That spoke volumes about where each of these two teams are going. The Colts are on a fast rise while the Texans are kind of standing still.
The Colts have a ton more money to work with this season. They went out and spent tons of cash in free agency and beefed up their lines and secondary something fierce. While the only real add to the Texans was an old Ed Reed that may or may not be healthy. And that rookie Colts team will no longer be rookies. And the Texans have a tougher schedule. The Texans for example have to play the Patriots while the Colts don't.
All the meanwhile, the Titans have a descent quarterback and are improving. And the Jags while they lack a good quarterback, did improve quite a bit in the draft. So the AFC South is rebuilding and getting tougher.
Whenever you hold the AFC South title, you win it. However, with the huge hit to the level of play of the AFC South and turnover, the Texans somewhat also inherited the title instead of having to beat out a tough division that during Manning's era won more games than any other division in the NFL and at times sent as many as 3 teams (AFC South Champion and both wildcards) to the playoffs.
I think people are over-estimating the quality of the Texans last year because they were #1 in the AFC for most of the season, although they kind of fell apart at the end of the season. Meanwhile they are somewhat writing off the Colts as a fluke due for their sophomore slump when they have a ton more talent, experience and money going into the 2013 season than they did going into 2012.