I'm a dirty Euro, but I've been following American politics on and off ever since 2007. I honestly have to say that Sanders is a breath of fresh air, as he accurately describes problems with both American and international policy that politicians generally ignore and he has done so for decades. His most important message (imo) is that democracy in America is hollowed out by the loose rules of the campaign finance system. I think it's ridiculous that corporations are able to insert money into political campaigns and influence elected officials that might depend on this money. Sanders is genuine in the sense that he doesn't have any big donors he needs to cater to. He has been consistent about his opinions for decades which is reflected in his voting record in Congress, and he actually has some very good ideas. I find it especially inspiring that he dares to stand up to both the financial and political establishment, while the odds are hugely stacked against him but still performs really well among voters. More politicians should be like him.
Now, I know there's similar problems in Europe, but I really wish there were people like him here who dared to question the political system, and aren't incredibly nationalistic and/or conservative. But maybe Sanders could inspire such a movement in Europe if he were elected.