I like both summer and winter. Just seeing people diminishes the feeling of loneliness in my case, so the summer is better since in the winter everyone is hiding in their basements.
The winter is cozy as fuck, everything looks beautiful and the feeling of coming home after a long cold day is amazing, but spending this time with someone would be better. In the winter you're reminded about the fact that most couples are having a hot bath while some kindles light up and create a romantic atmosphere. Most couples are wrapped in their soft coats while they are watching the movement of the flames in the fireplace.
They are driving together in their cars and having deep conversations while snowflakes are hitting the windshield. Is there anything more satisfying than that?