When I was a kid nobody but adults liked "educational" games. They were the highbrow equivalent of today's buying a massive electric Vespa to your 7-year old, with support wheels , just because it looks cool and you always wanted to have one, when you know that your kid will have more fun with a cardboard box.
My questions are: What do you want to achieve with an "educational" game? Is it compatible with being a game, something that people play for fun? I guess that you want the kid to "learn" something. What is it that you want the child to learn? Do you expect the child to learn it by playing with it? Would you have fun with it yourself? (naive as that might sound, remember that kids tend to imitate behaviours and their preferences might correlate with yours due to environmental and genetic reasons).
Having said that, I recently bought myself a set of Cuisenaire Rods , which were used in my classroom to learn basic arithmetic at that age :-) My adult self quickly found out how to calculate square roots with them.
In response to your questions: I want to get more math and science into his life. I think his school and our dad are both very literature heavy. Ideas so far have included Snap Circuits, tiny animal habitats, and plant kits. And yes, these are all things that I'm at least a little bit "Oh Cool!" about. Hes young for rockets and real electronics kits. I wish there was a more fun way to get kids going with math/logic/programming at a young age that they can eventually do on their own.
Those rods looks really neat. I don't know if they'd be game-like exactly, but, I'm now definitely glad I asked the question to HN! I wouldn't have found them otherwise.
You can find education just about everywhere. For example, I used Grand Turismo 4 on the Playstation to teach my older kid some basic physics.
My experience is that kids don't really learn much of anything if you just plop a game or toy in front of them and walk away. You have to engage with your kid and the game at the same level you want them to engage with it and you have to be an active participant. That's certainly true for the young ones. Once they get to 12 or 13 years of age they truly have the capacity to learn on auto-pilot. Some younger than that.
So my answer is going to sound a little snob-ish: The best educational gift for a kid is a parent truly engaged and dedicated to teaching them something, anything.
You know, at 7 they are just not going to concentrate on anything educational on their own unless it is insanely fun and engaging. You are the only one equipped to understand what might drive him because you know him and the environment.
Barring further information I'd say Lego's or something like a train set. He's still a baby.
I can easily imagine this being a story you could come back to again and again, getting a little more out of it each time as the reader gets older and wiser.
 First sample chapter: http://www.laurenipsum.org/mostly-lost