A couple of years ago, after an ill-fated attempt to run the mess that is Machinations of the Space Princess, and still wanting to give some science fiction role-playing a chance, we switched to Hulks & Horrors for a few sessions for our After Earth campaign. Unfortunately some fluctuations in our group put the kibosh on that game. The one thing that we did enjoy was the system of Hulks & Horrors. This is a great little game that, like so many in our super saturated RPG "market," didn't really gain the foothold that it deserved.
Sadly, there is still a strong "What can I buy now?" element to gaming communities that tend to drive a mentality of "what's next" commercialism. For better or worse, this means that game are bought and then never used before the next wave of games are bought (and not used). I admit that I've never really had a collector's gene (despite all the comics that I own), and the idea of buying things just to collect them, rather than to use them is rather alien to me. My only problem with this whole cycle is that we tend to end up with subpar, or uninspired games that are being produced solely to be put up on a shelf somewhere.
One of the reasons that I liked Hulks & Horrors was because it took the simplicity of a game that I liked (Swords & Wizardry Whitebox) and took out some of the things that I didn't like about that game. As much as I like the simplicity of Whitebox, sooner or later the whole all damage is measured in d6s starts to bother me. Hulks & Horrors isn't derived from Whitebox, so that isn't why I am making the comparison between the two games. In Hulks & Horrors, Berry went back to the open content of the 3.x SRD and then used them to create his new game, using the paradigms of older editions and an o school style of play.
Part of why Hulks & Horrors succeeded for us was because it was a lot less complicated of a ruleset than Machinations of the Space Princess, in fact Hulks & Horrors succeeded in capturing the old school simplicity that escaped Machinations. Where Machinations added a great deal of unnecessary detail to character creation and combat, Hulks & Horrors kept it simple and made for a much more playable game than Machinations.
Other than the spectacular art from Satine Phoenix, there really wasn't much to Machinations, or to the "Metal Hurlant" atmosphere that it claimed to support. While Hulks & Horrors doesn't claim to support such a style of play, there is also nothing that keeps you from playing this sort of campaign with the game. That is one of the appeals to an old school style of play, the lack of explicit support doesn't mean that you cannot use a game in that style. You can even take Hulks & Horrors sister game (using a variant of the same system), Arcana Rising, and use it to add magic to your science fiction.
From what you get in the game, I think that Hulks & Horrors supports a sort of classic star traveling science fiction with elements of the 40k Universe. You could very easily dial up the 40K-ness of the "setting" of the game with the addition of monsters and some back story. The existing classes (Pilot, Scientist, Soldier and Psyker) could easily be ramped up to support this. For Judge Dredd fans, you could easily reskin the classes to be departments of the Justice Department and run with it. One of the reasons that I like the Scientist class is because its inspirations are a mashup of Doctor McCoy and the Doctor.
Like many old school inspired games, Hulks & Horrors doesn't have an explicit setting. Instead the ideas of the setting are revealed through the details of the character classes, and through the monsters included. This is what makes games like this so easy to hack. For example, I would say that the one thing that Hulks & Horrors would not do as well out of the box is to support a Star Wars-inspired kind of game. You could add on to it to do that, Jedi-inspired classes are a dime a dozen out there on the internet, and because of the game having the commonality of D&D as the base, conversion is fairly easy.
So, really, this is a lot of words telling you to go back and check out an overlooked game that deserves more love than it receives. I think that it will pay you back with hours of gaming fun, and stories to tell your fellow gamers for years to come.