Aside from the real-world settings and a couple unique features, HAWX is a shadow of what Ace Combat 6 has already done.
I'll start with the technical aspects of the game. The visuals can be great, especially flying around real world environments like Rio de Janeiro, Chicago, Washington D.C., and Cape Canaveral. The planes all look great, with some nice effects like shockwaves as they go supersonic, and trails from the wingtips as you inevitably execute some barrel rolls. The audio, however, doesn't fare as well. The voice of the Ghost team you are covering in a couple missions can quickly get on your nerves, as it seems unnecessarily deep, raspy, and obnoxious. The dialogue can get really repetitive, such as the AWACS using the same phrase to call out targets again and again, and sometimes actual dialogue gets cut off or overridden by the regular 'background' chatter. There are times you will actually find that there is too much chatter, to the point where you tune it out to focus on engaging targets. Also, some missions spend the first minute or so on dialogue that could've been handled in the briefing, meaning you could be flying in the completely opposite direction for a full minute before you are actually given an objective.
Speaking of objectives, the missions don't often require much thought. Even on hard difficulty, enemies are sent at you in waves of 2-4, which are very manageable, especially when you task your wingmen from 'defend' to 'attack.' Unlike Ace Combat 6, where listening to the battle chatter will let you know which of the other units needs your help the most, there's no real need to pay attention to your allies in HAWX. Objectives are presented in a really linear order, and even on hard, missions offer little challenge. Continuing to compare to Ace Combat 6, some of the missions even follow the same pattern. (Possible spoilers ahead) For example, one large air, land, and sea assault on a city parallels almost exactly the first mission of AC6, including the false sense of victory until another 'elite' fighter squadron shows up to eliminate you. In another mission, you end up disobeying an order to disengage, similar to the desert engagement of the Strigon team in AC6. Yet another mission finds you flying through a canyon below radar to hit a special target. You begin to wonder, did Ubisoft simply play Ace Combat 6 and think 'oh, these levels are good ideas, let's use them in our game'? The storyline is even predictable in some parts - you just have a feeling that the private military contractor you work for in the beginning isn't an angelic group, and that you soon will be turning against them.
There are a wide number of missions, and although objectives start to repeat as time goes on, they are spaced out and in varied scenery each time. The number of aircraft available to you is huge, as you unlock more after each mission, however some aircraft could have been left out, such as multiple variants of the same jet. There is not a significant handling difference between aircraft either - an F-117 can do the same high-performance turns of an F-22, which anyone familiar with the jets or aerodynamics knows is impossible, but we'll get to realism issues later. The game nicely recommends an aircraft for you for each mission, but if you go back and play through the missions again, it recommends the same aircraft the second time around, even if you have better aircraft unlocked. Of course you can still choose whichever one you want, so it's not really an issue.
Ok, let me preface this paragraph by saying yes, I know this is a game, and they often require suspension of disbelief. But Tom Clancy games usually strive for realism, albeit sometimes a futurized version, and being a pilot, some of these issues bothered me even more. Let's start with handling - the OFF mode allows you to perform extreme maneuvers that are realistic (you can't 'drift' in aircraft like you can in a car), however the fun of executing these tight turns and flips balances out. In one mission [spoilers?], you fly an F-117 to within 200 feet of the ground on a rollercoaster of a bomb run, dropping dumb bombs. When has a nighthawk ever flown that low to the ground - did I mention you're flying on your side? - and why wouldn't it use smart, laser-guided munitions like it was designed to do?? And not only are you essentially saving the world single-handedly, but you never even get promoted above the rank of captain for doing so? Also, what kind of suicidal lunatic would attack a country like the United States with a single company's private military force? There's now way they could expect that to work out.
I'll end this review with a few lingering issues I have, and returning to the sentiment that this game can be fun, but isn't one that you should spend much money on.
-You develop no attachment to specific ground/ air units like you do in Ace Combat 6, where you become familiar with each callsign
-Again, there is no high-G turning like in AC6 unless you go into 'OFF' mode, which completely changes your view and can make targeting difficult
-The ERS doesn't seem that effective - I find it usually easier to handle dogfights on my own than by following some tricky path that takes too long and usually has turns that are too tight
-While you are almost guaranteed to not run out of ammo, there was a certain fun in being able to land to resupply in AC6 which can't be found in HAWX
-If you're really into collecting as many achievements as possible, 26/50 achievements in HAWX are from multiplayer, which is bad news if you don't have the fastest internet or can't find any games once everyone has moved on
-Extremely anticlimactic ending leaves you wanting a more satisfying end to the game than what your final mission is...