The answer is yes. The house is designed to always win. In a casino game like Roulette, this is through having zeros, but offering odds as though the zero doesn't exist, so it's a small enough house edge for punters to still be able to win often enough to make them want to play, but large enough for casinos to, providing they can play a sufficient volume of hands, to win.
In Sports betting, the house edge is slightly different. In any given even, say a football game, the house edge, or 'overround' is factored into the prices offered, such that if a punter was to back all the outcomes, they would lose. Put numerically, if a football match had equal chances for the home win, draw, and away win, the likelihood for each would be 33.3%, giving decimal odds for each of 3.00. A bookmaker would therefore offer the price for each of say 2.90. Therefore if you backed each of them, you would not win.
HOWEVER, with Sports betting, there is clearly an opportunity for the bookmaker to price things incorrectly. Therefore even though backing each outcome of a football match 2.90, if the match was between Manchester United and Accrington Stanley, the Manchester United win side of this bet represents good value (assuming it's the first team playing).
Bookmakers will not get every price right (not to mention that you can shop around). They should be better at getting the prices right than the average punter, since it's their job, but that doesn't mean they always will. And so long as all of the markets they offer in aggregate offer a return, they can get away with getting the value of an individual market incorrect. This is where value bettors make their money.
Tony Bloom is arguably one of the most successful value bettors of his generation. Starting off as a small time punter on the 1X2 (home win, draw, away win) for football matches, Tony soon became so successful that Victor Chandler whisked him off to Gibralter with a job offer. As part of the Victor Chandler shop, Tony went out to Asia, where he learned about the Asian handicap market, which at the time was unheard of in the UK. And the rest, as they say, is history, with Asian handicap betting now available across all the bookmakers in the UK. But that wasn't the end for Bloom. After falling out with Chandler, Bloom initially set up his own bookmakers Prembet, although this didn't seem to take off. Now, Bloom owns Brighton football club, has played in the final of the World Series of Poker, and also runs a covert betting consulting operation called StarLizard.
So, does the house always win? Yes it should do. But the point is, so can individual punters. The house is playing against the aggregate of all the punters. As an indivdual, if you can find value, you can WIN.
We do not recommend adopting a value betting strategy without thoroughly understanding the approach, therefore continue reading before jumping straight in.