If you like the Racer 5, try some of the other west coast IPAs--maybe be you like those more piney IPAs more than the more citrusy east coast style ones.
A few good ones are:
Green Flash West Coast IPA
Russian River Pliney the Elder
As for the Guinness Black Lager, I didn't care for it either. Pretty bland. But I'm not a huge lager fan in general, and don't think I've had a black lager I've liked. So it's probably more that I just don't like the style rather than it being a poor example of the style.