I dont think this thread should be "What decade" but rather "What year in the 70's had the best basslines?" Personally going by release dates I'm going to say 1973 mabye 74 AJ
Let's not forget the "Mighty Entwhistle!" But overall, in the 60's and 70's recording companies at least seem(ingly) let an artist develope themselves over a few records before they were successful, or dropped. Which IMO, lead to some experimentation, and developing of style(s). Nowadays, it's one shot and you're in or out. Roxy Music had their best stuff in the 70's. IMO.