Funnily enough, I like Space Adventure COBRA nearly as much as I like Lupin! I decided to watch COBRA after I found out that Yuji Ohno, long running composer of the Lupin series from the red jacket show onwards, composed the theme song to COBRA. Both shows are quite similar in a few ways. Like COBRA, Lupin is a bit goofy and things don't always go right for him, but he still manages to be cool as heck at times. The humour is similar in both shows, and while COBRA's story continues between episodes, the green and red jacket Lupin shows manage to be just as gripping, even as standalone episodes.
If you liked COBRA, I highly suggest you check out the green and red jacket Lupin shows. Green ran from 1971 to 1972 and has 23 episodes. Red ran from 1977 to 1980 and has 155 episodes. Since the episodes are standalone, you can dip in and out. You wont regret it. I wouldn't advise starting with Fujiko Mine, as the characters and tone of that show are way different than usual.
Also, I have to admit, as much as I love the 1980's COBRA series, I'm not a huge fan of the original film and the modern stuff. They just didn't compare IMO. Also, another note - the Japanese voice actor for Crystal Bowie also voices Jigen Daisuke, and has been for 40 years.