Sansotei is my favourite place in Toronto for ramen, bar none. Although the lineups can be long, the wait is worth it. My go-to is the spicy tan tan which hits the spot in terms of heat and flavour. I usually get it with thin noodles as I find it makes it easier to eat.
Be prepared to share your table with other diners, this restaurant is very small so communal dining is a thing. They do tend to turn the tables quite fast, however, so musical chairs is unfortunately a necessity during busy times.
Other popular items on the menu include the tonkotsu ramen and zangi (chicken karaage) which are both amazing in their own right. Personally, I like things spicy so have not ventured past the tan tan.
If you like ramen, go here immediately. Others might imitate, but Sansotei is the best in the city by far!