I'll start with Hall & Oates. I knew the odd one or two of their songs without knowing it was them and then it wasn't until I got into Private Eyes, then I checked out what else they'd done on Spotify and found a load of their other stuff and that was when I fully got into them, I imagine them to be my driving playlist (when I eventually do start driving that is) because of their prominent rhythms throughout their songs and sing-along-ness of them
Next is Marvin Gaye. He's simply a soul legend. If there is any artist that you want to play for a cheeky evening with a girl, he's the man. Just listen to him, What's Going On, Let's Get It On etc, and even his early stuff with Tammi Terrell is still top.
Next, The Four Seasons. Only recently got into this since realising that they sung Beggin' and then realised that they sung a shed load of songs that I didn't even realise. The voice of Frankie Valli and the songwriting of Bob Gaudio created a sound that lasted a generation and still can be heard now and still everybody knows their hits. I don't think there has been anyone or ever will be anyone who has the vocal range of Valli and have the quality and power in the Falsetto range.
Finally, we will have the only modern artist that I can listen to a full playlist of, Plan B. His most recent album, The Defamation of Strickland Banks is actually pretty decent for something modern. Because the album tells a story through the songs, all of the songs lead onto one another and there is mixture of soul and rap so it mixes it up a bit which is good for those who get bored of the same sound going on and on for 50 minutes. So yeah, if you want something modern, get on it.