I respectfully disagree, mate. Personally I think there are some film series' where the sequels really don't deserve the same artistic and celebratory treatment that the original films rightly receive. The Jurassic Park and Rambo films are good examples of this. I'm a massive Jurassic Park/Rambo fan and I unabashedly adore the sequels that have been made... but they just happen to be two franchises where only the first film is a true classic if we're being honest (though I do really like the Mondo poster for First Blood Part 2) - Now I also think that the Back to the Future sequels are not as good as the first but with that series it obviously all feels of a piece - thus it makes sense that Mondo eventually releases The Back to the Future trilogy and not just the first film on it's own. Star Wars is another example of a franchise that is of course a story told in three parts essentially, so it would be strange if we got a Mondo steelbook for Empire Strikes Back and not for Return of the Jedi despite any percieved difference in quality.
With Indy... I'd love a Raiders of the Lost Ark steel but I think it would diminish Mondo if, say, they made a steelbook for Kingdom of the Crystal Skull just for the sake of... completing things. With Terminator... Rise of the Machines doesn't deserve the same attention as the first two films. I'm a fan of the Halloween franchise but the first one is the only one that should have the Mondo treatment. Same goes for Robocop, Predator and Jaws. Mondo steelbook for The Godfather 3? Nah. Alien and Aliens, sure! Alien Resurrection, meh. No thanks to a Rocky 5 Mondo Steelbook. I could go on and on with examples really. With Mondo's steelbooks I think there has to be a shift away from that normal mindset of... "Oh, if there's a steelbook for the first film then I obviously want one for the second one as well. The display shelf would look odd otherwise." - When it comes to franchises only the very best entries in those franchises should be considered.