I don't mean the brand of the beer they sell. I mean the condition they serve it in.
Too many places I've been to and the beer has been watery, headless, head covered in spots e.g off, or tasted down right funky, etc.
Ahhh, now that is an issue. Sounds like either a lack of sales or bad cellar management. The thing is lager and commercial cider is very easy to keep, as long as you clean the pipes regularly you just change the barrel when it runs out.
Real ale on the other hand you need to have the casks ready on a stillage, vented and taped at least 24 hours before the beer goes on sale. This takes prior planning put your beer on too early and it's starting to spoil and is already past it's best. Put it on too late and it beers not ready, the finings haven't had time to do their work, and the beer is dull and cloudy.
The other thing is the beers you put on sale, in the pub where I've worked we've sometime kept beers off sale. The reason being is we've got a similar less popular beer on, and we need that to sell out first.
To do beer well a landlord needs to be in his celler every day, he needs to train his staff properly, and he needs to employ people who know what beer should taste like. Where I worked beer would never go on sale unless someone had tasted it first.
EDIT: Another issue is line cleaning, proper real ale will have finings in the bottom of the barrel. Some of this will get sucked up when the barrel runs out, so the lines need to be cleaned with water ever time a barrel is changed as well as a weekly clean with a chemical pipe cleaner.