Best New Haven restaurant
Well, Union League Cafe has always been the touchstone of gallic food in New Haven. If you are willing to consider other cuisines, Ibiza, Zinc and L'Orcio are certainly worth a mention. And not too far away, Le Petit Cafe in Branford has a highly rated French menu and a devoted following. And a half-hour to the east, Cafe Routier in Westbrook has a three-part menu (one section of which is usually French or continental).
Union League Cafe is you best bet for french, excellent food, great service, old school classy.
Ibiza is spanish, also very good.
and for interesting, it would be hard to beat Thali, great high-end indian food with lots of regional specialties that you don't find on typical indian menus in the US.