As i sit here in my Motorhead tour t-shirt I can proudly say Bomber is my personal fav. Whoever said No Remorse has a good point, all their best material is right there! And yes, No sleep to Hammersith is their definitive live album too.
1916 baby, but it's definitely a very closely run thing. Ace of Spades IS an excellent album, but 1916 tops it very slightly by having a better production, and more diverse song writing.
Ace of Spades would be the cliche answer, but I personally like Bomber better. And I have not heard anywhere near all their albums so I really have no idea what else is good or not (apart from Overkill).