http://www.techtree.com/India/Techtree_Notes/Serious_Sam_3_Human_Side_Of_The_Headless_Kamikaze/551-115526-889.html

I never finished SS2, it lacked something that made SS1 so great. I think it was the simple levels with lots of enemies and relatively short play time. SS2 was too busy, levels too small with lots going on...plus it crashed about 80% through and lost my save data...