Simple answer: Yes
Smoking or consuming marijuana before sex can increase how much one enjoys sex.
This is for a number of different reasons.
Marijuana doesn't produce serotonin but it does affect a chemical in the brain called anadamide, which causes soothing sensations in the body when it reacts with THC. Mj also affects dopamine, a neurotransmitter involved in the brains pleasure producing mechanism. These 2 combined can lead to better sex.
Its relaxing. Personally I feel more relaxed when I smoke, which allows me to let go, which leads to better orgasms.
Its fun, which can lead to the giggles, and if you have never had giggly sex you are missing out.