It's football and then nothing for a long time. Hockey, basketball and handball are similarly popular and it depends on the area which one is more visible. I wouldn't even bring up sports like ski jumping or biathlon because those events occupy public consciousness only for special events like the Vierschanzentournee or the Olympics but otherwise are irrelevant. During Olympics anything can get ratings provided Germans are contending for medals, it says nothing about the sport's popularity in general.
The only sports that really exist as professional leagues with solid spectator numbers outside football are handball, basketball and hockey. Hockey I believe is the most attractive sport out of the lot but it faces an uphill struggle as even if you enjoy watching it, it's a struggle to play it. Rinks aren't very common and equipment is pricey. Basketball and handball on the other hand are popular sports at the school level, don't require special equipment or a special surface. Not surprisingly Germany is more competitive in those other sports than in hockey and thus viewership and media attention for international tournaments is much bigger. It has to be pointed out though that the leagues in all three sports had to fight for their TV presence as really only football is guaranteed a spot, so hockey's lot is shared by basketball and handball in that regard.