Sauté onion, green pepper, and garlic in olive oil in a large Dutch oven until tender. Stir in next 9 ingredients, and bring to a boil. Reduce heat; simmer, uncovered, 2 hours, stirring frequently. Add crab meat, stirring well. Simmer, uncovered, an additional 20 minutes, stirring frequently.
Cook spaghetti according to package directions. Remove bay leaf from crab sauce, and discard. Serve sauce over spaghetti, and top with cheese. Garnish with parsley, if desired.