Absolutely - all the series credits say "Characters created by Sylvia Anderson".
So between them, all the credit that is given just to Gerry should be shared with Sylvia, and Derek Meddings and Barry Gray, and a few others as well, but those were the most indispensible.
Remember, Anderson tended to keep most of the same people from one series to the next, so arguably it's the whole team who should get the credit.
I guess that answers the question of what the producers and executive producers do on TV shows and films - they take the credit for everyone else's hard work!

And don't forget old Sylvia Anderson, who from everything I've read, sorted out a lot of Gerry's storyboard/character problems, and kept things ticking along.
Another case of a wife/husband team where the wife is forgotten.

Don't forget the sound editors. This group never bacame houseghold names, but without the expert editing and mixing, none of Anderson's creations would be believable. Form the guy who programmed all the lip-flaps on down the line to the re-recording mixers, everyone deserves kudos for clean and powerful soundtracks that brough all the fantastic images to life.

Oh yes, definately. The series are about forty years old now but the effects are still breathtaking. As for Barry Graythe Thunderbirds March. Nuff said.