Hmm, that's a bit odd. Slow cooking normally produces very tasty meat. What kind of things are you cooking? I never follow recipes to the letter - don't be afraid to add extras!
Firstly, are you using cuts of meat that are meant to be slow cooked - so, for example, with beef: shin, flank, skirt, silverside, brisket. Basically, the cheaper, tougher cuts are best, as a lot of the flavour is in the sinew and muscle. Secondly, what other ingredients are you putting in? You need to work a bit to get a really rich stew, for example. Use a decent stock and add a good splosh of red wine. Marmite or Bovril are brilliant added to stews to give a rich, deep flavour, ditto a splash of Lee & Perrins. Do you use herbs and spices?