Both! It is all dependent upon attitude. If you feel resentful about HAVING to please others, life won't seem enjoyable. If you enjoy pleasing others the joy is in the doing. Remember, it is very easy to please others: a smile as you pass a stranger, a "hello," to a neighbour, giving up your seat to someone infirm on a bus or train. Doing this makes both you and the receiver feel good. The rewards of the spirit are often immediate.
However, probably the best way to have a more sustainable and relatively constant life of enjoyment is to serve all doing something you love doing; something you're happy to do for 'free.' Then you'll forget about little ego's wants and be coming from that BIGGER part we all have. And that's a part of us that IS joy, love, compassion and all of the good things inside.