They sound very like Tangerine Dream

I would prefer to suggest that no one, sounds like TD, and no one has really transformed and learned the synthesizer from DAY 1 to the day that Edgar Froese died, like they did. 

Many of the folks mentioned did not have the "symphonic" sound (as I call it) that TD had, which they developed further yet, in the 90's by adding Linda Spa and Iris Camaa and later Yoshiko. In the last 5 of 6 years, the performances on DVD show how clearly well rehearsed and develop their music is, and the layers of it, only rivals someone like Klaus Schulze that has so many layers going at one time, that it can drive you silly trying to work them out.

Some folks, like AshRa Tempel (later Ashra), Cluster, Popol Vuh, Namlook, Gottsching (he is.was Ashra Tempel and Ashra), Grosskopf, neuronium and others, were in the early days, quite experimental, and it was something like TD's ATEM, and then PHAEDRA, that immediately showed a melodic/classical style of using the synthesizer, and very few folks have really worked on properly and with dedicated reason. I would suggest Larry Fast did really well, and a few others ... however, comparing all of these is a very difficult and time consuming exercise, that kinda starts and ends with them using the same equipment, however, only two folks, really went out of their way and everyone else's to do something with it that no one else did ... and they were TD and Klaus Schulze.

I, personally, do not like to exclude something like the Cosmic Couriers, because they took this style and expanded it to rock music, although so much of it is mentioned today as some kind of drug trip that the folks that put it together did not realize was going to be released ... something that I find a bit weird, but there were, in there, some wonderful things that stand out, even then complete different from what KS and TD went on to do, but in those days, of early Ashratempel, LS was a part of them, and later the first several albums without KS were also magnificent (specially New Age of Earth), which kinda gave away the cleverness and the use of the synthesizer, that had its mechanics so well "disguised" (not really, just well designed unlike Dave's suggestions!), whereas the use of the instrument is much "simpler", and yet it comes off very well and setup beautifully, specially on that album! 

The majority of those folks, remained an experiment that never went away, and many of them, specially Brian Eno, were outstanding, and came up with completely different things, that were not exactly synthesizer defined or designed, specially in loops and their integration, something that KS went on to develop to an insane level ... catch the DVD that has an interview with his and some engineers, working on a segment in one piece, that you and I would not even notice! It will show you the layers and how well developed they are, and how much more some of these can be fooled around with.

JMJ fits a different mold for the synthesizer. I consider him a "classical" musician, except that his orchestra is a bunch of synthesizers and he has developed some wonderful pieces of music that stand out and sound magnificent, but unlilke TD and KS, he is not an originator of the instrument, although he is one that helped show how well you could use the instrument to create various layers of "classical music" on your own piece of music. 

I like to suggest that the really early ones, the experimental ones, are more than anything turning a "knob" slowly. Remember that in those days, that sound was so new and experimental and the idea was to feel that sound and how it affected you, which of course led to a series/sequence of sounds, that we call ... MUSIC. Today, no one, not even Dave, is capable of doing that and making it last and an important part of his music, which like many of his contemporaries today, is defined and designed around a beat, and not necessarily the sound itself.

And that "sound" feel and study, is the difference. If you are into the sound and feel of it, you will be looking for a lot longer, because many of these suggestions won't quite fit, what you might be looking for. If you are looking for a sound that is somewhat classical in its compositional style and sense, then the number improves, and TD is probably the best there is in that department. I think Larry Fast fits also, but the rest I am not so sure they fit, although I admit not listening to them as organically and energetically as I do these more important ones. For example I do not  dislike Pete Namlook but his work is not nearly as valuable or important to my feelings as some think. Maybe his style just did not click with me, but it feels "industrial" and "controlled", as opposed to the originals, that you hardly could tell where the sound was going, even if this knob only went this way (and some folks like Dave know it!), and it took 3 minutes and its sound in between was fiddled with even more! Namlook, for me, was too mechanical, and TD, even though they were the SEQUENCER kings, and probably the ones that developed it the most and best, was never that mechanical, specially sound wise ... the music continued to develop, even if a theme returned.

Not sure I can explain my feelings on all this any better ... my apologies if the wording seems somewhat confusing, but this is the best I can come up with.