My list.
SR2: To this day Stilwater looks beautiful. Loads of hidden Easter Eggs, some actual variation in character models, and NPC's that react in a more natural, organic manner. (With the exception of their constant desire to run over the Boss). The story is pretty great offering a balance of tragic moments, high-action raids and all around hilarity (such as the side mission where you sprayed buildings with feces). Tons of side missions. (However the fact that three of the most needed upgrades were tied to Heli Assault and Red Light Escort was kind of annoying). Great character customization which was made even better with the console exclusive DLC and the PC exclusive Gentlemen of the Row Mod Pack, The radio selection is pretty solid too, from 80's rock, to 70's funk to 90's\early 2000's rap, RNB, pop and techno\industrial. However graphically speaking you could tell it was one of the earlier titles for the 360 and PS3, the vehicle handling was meh ESPECIALLY with the sports cars and "heavy" vehicles, and the enemies only really consisted of basic grunts; with the only major difference being the clothes, HP and voice-lines. It's still a great game even with these faults.
SR3: This was one of the games I grabbed for the PS3 and later on the PC alongside SR2 when it first came out. Needless to say I loved it. Gun mechanics were better, the vehicles didn't handle like greasy cinder blocks, and the missions (or rather the main missions) were far more energetic than SR2. Other than the standard upgrade in graphics there is far more enemy variety than in SR2. From riot cops, to tanks and helicopters, to hitmen armed with sniper rifles, grenadiers equipped with slimmed down EOD suits, enemies that can teleport and even a small army of minigun (or even flamethrower) toting supersoldiers. Lastly I really like the new upgrade system, just wished you could toggle some of the upgrades on or off. However that's were the compliments end and the criticisms begin. For one let's get it out of the way, there is less customization the in SR2 when it comes to clothing. From what I heard this was due to THQ breathing down Volition's neck to get the game out as fast as they can despite the fact that they were working with a new engine. Melee combat was dumbed-down, for some reason you can no longer store the Minigun, Flamethrower or Sledgehammer in your inventory, the day-night cycle was removed, there are far less Easter eggs, civilians look far more generic consisting of almost exclusively fat businessmen, teens in hoodies, hipsters, bums and construction workers plus the reactions from civs are far less lively than in SR2, most of the dlc is just awful and some of it was actually content pulled from the game (great Capcom impersonation THQ), side activities such as FUZZ and Fight Club were removed even though you meet an ex-FBI operative and a wrestler, instead we get escort missions repeated ad-nausem with the only difference is that you're either in a car, helicopter or actually driving someone around the city, and the biggest elephant in the room is Steelport itself, oh sweet lord, is Steelport just mediocre. not only is it noticeably smaller than Stilwater but outside the Airport, Burns Hill, Downtown and New Barnec the city is just a bland boring mess of factories, slums and mid-rises. I get that Volition wanted to create a more down-trodden industrial city with some Cyberpunk elements but we can clearly see that in the concept art the city was supposed to be far more detailed then what we got in the final product. Here's a link to said concept art BTW.
Arapice Island-
http://vignette4.wikia.nocookie.net...tskirts.jpg/revision/latest?cb=20120827231851
Downtown Day-
http://vignette2.wikia.nocookie.net...elport3.jpg/revision/latest?cb=20120828002707
New Barnec-
http://vignette2.wikia.nocookie.net...elport5.jpg/revision/latest?cb=20120828003338
Simply put I love SR3, but you could definitely tell it was a rushed game.
SR4: SR4 is a rather odd game for me, I love yet at the same time I don't. First let's start off with the good. The superpowers are amazing, the collectibles are addicting in a sort of crackdown kind of way, the story is less schizophrenic than in SR3, you can change the pitch of your characters voice and the weapon customization is much better and they added in a decent amount of clothing. However there are a large amount of problems from SR3 that haven't been fixed. The reason why I'm saying this is that several of the major complaints about SR3 is that the activities lacked in variety, the city was a bland bore outside of a few key areas, the dlc was bad, you couldn't toggle any of the upgrades on or off and the story as wacky as it is, somehow ends up being very predictable. So in SR4 instead of having a dozen flavors of escort missions we have a dozen flavors of blow x amount of stuff up in y period of time, you still can't toggle any of the upgrades on or off after you buy them, the clothing DLC is
a lot better than in SR3 but they still charged you for cheats that still flagged your save and instead of three mid-length story dlc's like SR3 we get two extremely short story dlc's that can be completed in under an hour, the story is less "hurr-duur lets be wacky" and more "random pop culture references thrown in under the wafer thin guise of parody". This all leads us to the main reason why I don't like SR4 nearly as much as the previous entries in the series. First let's start off with the enemy variety. For this we'll have to talk about the plot. In SR4 the Boss and company become world-famous politicians after defeating a small terrorist outfit\arms dealers in an unnamed middle-eastern country and subsequently stopping them from launching a nuke at DC. however this somehow catches the attention of the intergalactic empire known as the Zin, Who invade earth, abduct most of it's population and forces them into matrix-like simulations of various cities including Steelport. Now with this concept and Volitions love for parody they had a goldmine of opportunity for enemy variety. Just imagine fighting humanoid shock-troops like the Combine from Half-Life 2 or the Tau from Warhammer 40K, religious zealots that serve as a parody of the Covenant from Halo, hive-mind parasites that could've been used to mock the Zerg or the Xenomorphs from aliens, or maybe even a mix of mechanical drones, humanoids, sterile engineers, and heavy brutes like in XCOM or Mass Effect, or... just use generic grey aliens in metal tribal gear. Heck they could've even used the whole Matrix theme to reintroduce the past gangs for more than a few missions or use the "virtual reality" theme as an excuse to introduce more "out there" gangs (steampunk, medieval fantasy, zombie, futuristic etc). Lastly Steelport believe it or not is even worse than it's SR3 incarnation. Most of the distinguishable landmarks were replaced with more dull generic buildings. This makes absolutely no sense as to why they did this especially since game uses the same engine as SR3. Don't get me wrong I like the game especially the PC version since it has a slew of mods that fix most of the problems I mentioned above but there's a reason why I like the previous entries in the series better than SR4.
SR GOOH: I'll admit I haven't played this game yet, the concept was pretty interesting but I was immediately turned away by the fact that it ditched one of the SR series strongest gameplay features and had one of the most tacky, anti-climatic endings to a story arc since Mass Effect 3. You know the one, the infamous "Dex Saga". Before you say that's just a spin-off like Far Cry Blood Dragon or Mothership Zeta, it's not. It's actually been confirmed to be part of the SR Storyline. I think Fl1ppy summed up the game perfectly in this video.