Yes sour beers were originally spoiled batches. But like anything, we started to drink them and develop a taste for them because deep down, we hate ourselves.
In Canada there aren't many regular sours on offering they're usually seasonals like Berliner Weisses which are okay but are pretty one-note when it comes to sour beer.
The best one that I could recommend that may be available in Calgary is Driftwood's Belle Royale:
http://beeradvocate.com/beer/profile...?ba=JonnyBeers
Very good sours are usually very complex in flavour. You get an initial sour hit followed by a good amount of fruit and then if the beer's been aged in barrels flavours of the barrel like oak or wine etc.
The best sour I've had is probably Supplication by Russian River. It is a truly special offering. You wont be able to find it in Canada, but next time you're down in California ask around for good bottle shops and you may find a bottle.
http://beeradvocate.com/beer/profile/863/22227
If you're ever down in Portland than Cascade Brewery is a must visit for their lineup of sours.