I'll pitch in my $0.02 here, since I'm a big fan of the miniatures games (both Fleet Battles and Ground Command) and because I'm a big fan of the background/fluff/lore.
A lot of this is subjective. What one gamer considers simple, others may consider complex. And not all games appeal to all gamers. GW and Privateer Press products are sold in almost every single game store I've ever been in--sometimes in multiple stores in the same town--and they have fans worldwide, but they don't appeal to everybody. So saying that a game is too simplified and doesn't have a "fun factor" is entirely an opinion. To which, of course, everyone is entitled, but it is mere opinion.
I can tell you why I think both the Halo miniatures games are fun, but again it is just my opinion. I like Fleet Battles because the models are cool and the mechanics just *work* for me, and because I really like the background. Ryjak, you talk about the boarding mechanic kind of being a dealbreaker for you; but for me, I think that it is highly cinematic and fits with the background of the game. (On a side note: I don't keep statistics, but I would bet that about 75% of the boarding actions that have occurred on both sides in my Fleet Battles games do not end up in a critical core breach. It is not a guaranteed outcome. If anything, the boarding actions tend to drag on for a few turns, which again I think is very cinematic and fitting.) I also like Fleet Battles because the ships tend to be less fiddly to move (Dale hit the nail on the head about FA frigates). And, to me, it just looks sweet on the table. There are other things I like about it, but I won't go into all that here.
It's understandable, however, why some people don't like it; probably for some of the same reasons I don't like Star Trek: Attack Wing or Malifaux. They just don't work for me, and Fleet Battles just doesn't work for some people. No harm, no foul. McKinstry, your point about the game only having two factions is well taken; there is room to flesh it out and include other factions (I can think of at least three possibilities--the Flood, the Sangheili, and human insurrectionists), which is something I hope Spartan does soon.
I like Ground Command because I was a huge fan of the console games and I believe that Spartan Games has faithfully recreated the characters and vehicles from the source material, and has recreated the feel of combat in the Halo universe--as much as you can do that when you translate an electronic game into a physical tabletop game. Much like Fleet Battles, gameplay is fast and vicious, again replicating the console games. I don't play many infantry-based games, and the other two I do play are DeepWars and (very rarely) Dystopian Legions, so I don't really have anything to compare it to. But for me, again, it just *works*.
Something else that really works for me is the "alternating activation" mechanic that Spartan uses in all their games. I much prefer that to the "you go, I go" system that GW (and other) games use (I think that's what it's called).
None of us has any insight into the inner workings of Spartan Games, so I think it's a little premature to say that the Halo games have "killed" Dystopian Wars and Firestorm Armada. Indeed, fundraising for the Dystopian Wars Kickstarter went very well; whether or not they deliver on time remains to be seen, but that sort of thing doesn't bother me too much--this is a hobby, after all, and I certainly have plenty of other ships to paint/game with while I wait on my pledge rewards. I think Andy's statement above about how Spartan does business is spot-on; they have pretty much always been feast-or-famine. Not all gamers are used to that, and not all gamers like it, but that's how they are. Spartan's business model has been dissected, discussed, hashed, and re-hashed ad nauseum on countless forums and in countless gamer conversations. It is what it is, and if that's not your particular cup of Earl Gray (I'm speaking of the general "you" in this case, not you personally, Ryjak), well then there are plenty of other game companies out there with which you may find more enjoyment. I'm a big fan of Spartan's products, and even I get a little annoyed at how they do things sometimes, but it has never diminished my enjoyment in playing their games. But...again, that's just me, and I'm willing to put up with it. Some people are, some people aren't, and there's no right or wrong in either opinion.
Happy to further discuss any of the points above.