the key to exercising long-term is doing what you enjoy.
Over time you'll go through phases and you'll enjoy one thing more than another and then later you'll start enjoying something else.
The general rule of thumb between cardio and weights is that cardio will help you burn a maximum number of calories during the workout itself, and will improve your cardiovascular fitness (heart and lungs).
Weight training also burns calories during the workout (but not usually as much as cardio unless you go real heavy and do lots of sets) but also helps raise your resting metobolism (the calories you burn just sitting around and doing day to day stuff).
The other great thing weight training does is help tone and shape your muscles, which when you burn off the body fat gives you that athletic look.
For maximum weight loss and good health you should try to include cardio, weights and stretching in your workouts.
What the balance is between these in your routine will depend on what you enjoy, what your goal is (short and long term), what injuries (if any) you have and what time and effort you are prepared to put in.
When it comes to exercise, the most important rule to remember is:
"It doesn't matter what you do, it only matters that you do!"
Keep doing what you're doing and experiment with other things when you feel like it.
When things become too easy, try to increase the intensity of your workouts a little and mix things up.
And keep having fun!