Sometimes I think people are a bit too harsh on the Sonic Series as a whole for the faults of only a few games out of a rather massive pool. Considering how the Duke Series is, it's kind of like the pot calling the kettle black.
To those out there saying Sonic only had 3 or 4 good games - you're being a bit unfair, don't you think? Especially with a franchise that has had over 17 games... People only focus on the 3 main Genesis games it would seem. I remember having a lot of fun with the GameGear Sonic games such as Sonic Triple Trouble, and Tails' Adventure as a kid, and Knuckles' Chaotix on the Genesis, Sonic CD, Dr. Robotnik's Mean Bean Machine, Sonic Spinball, and so on.
While I'll always love the original Sega Genesis/GameGear games that I grew up with in the 90s, I don't mind some of the 3D Games. Sonic Adventure 1 and 2 were fine in my book, they did have a few flaws obviously, but they were more than tolerable. Sonic Heroes was a disaster, I will state that in all honesty, but still wasn't as bad as 06. Shadow the Hedgehog could have been good if they cut the cheese factor with better dialogue/voice acting, some refinement & polish, no censorship (it used to have red blood, but they ditched it for green), and less buggy and glitchy BS. (I've clipped through the floor one too many times.)
Many non-3D Sonic games of recent times have also been enjoyable to me, such as the Sonic Advance games, Sonic Rush, and Sonic Battle.
It's worth noting that the Sonic Series is Sega's experimentation ground. They're always trying to take it in different directions, some good, some terrible. They do however, learn from their mistakes, if not a bit slowly. A good example of this is recent - after one particularly horrid and terrible game(Sonic 06), and several mediocre ones (Sonic Unleashed, Sonic and the Secret Rings, Sonic and the Black Knight), they have refined things a lot, and released some good games. (Sonic 4: Episodes 1&2, Sonic Generations, Sonic Colors, Sonic: Lost World.) I'm also going to go out on a limb to say that even Sonic Unleashed's daytime levels were fun from time to time. The night levels indeed sucked however. On the other hand, we have the Sonic Generations Unleashed mod to remedy that, which dumps those levels entirely.
Unlike some rabid Sonic fans, I don't get bent out of shape and curse new Sonic games based on trivial shit such as "OMG SANIC HAES GREEN EIES, IS GUNA BE FAIL GAEM!" (People like this seriously exist, and I swear they're the most awkward, psychotic, nostalgia-glasses-grafted-onto-their-face type of beta-males you'll ever see.). I like the modern Sonic visual design over the portly appearance of classic sonic (sue me), and despite what some may argue, his artistic appearance has no way of giving any sort of bearing on the quality of the core game. I do however have some things on my wish-list for the designs... more on that later.
Looking at Sonic Boom, I'm looking forward to how this game is going to turn out. They have some good people working on it, such as ex-Naughty Dog staff who worked on the early Crash Bandicoot games. The new character designs are a step in the right direction, but there's still something off about them to me. I like that Knuckles actually looks like the strong, beefy tank he's supposed to be... it's just that the proportions are off to me.. Something needs adjustment. Tails looks great as usual, and Sonic look is also good too... It's nice to see that they're starting to make it look like he actually has some wavy quills rather than 6 or so massive spikes. I just wish they'd extend his body a bit to even it out in proportion with his longer legs however...
(Speaking of Naughty Dog... do the redesigns remind you of the transition between Classic Crash -> Mind Over Mutant, except a bit less drastic? or am I the only one?)
Now about that wish-list of design changes: One thing that would *really* please me is if they finally got rid the "Visor Eyes"... you know what I mean, the "One Eye, Two Pupils" thing. Either make the characters have eyes like Tails, or at least bring the bit between the "eyes" down a few inches to close the gap. It's just something that has bugged me greatly for some reason. I'd give anything to see them get rid of that part of the overall Sonic character design.
Another thing I'd like to see, is for Sonic's quills to have some level of detail, perhaps with the help of alpha-maps. Still keep the same iconic and cartoonish design, and still have the overall shape of the big spikes, but instead of just solid-colored spikes, they are stylized groups/clusters of millions of quills that taper off to a point. Of course, modeling those quills with polygons would be impossible, thus why I mention alpha-maps. (Or perhaps a nice hair shader like seen in some Square Enix games, but with much thicker and stiffer strands.) I have a good-looking example of it in my head, and wish I could explain and demonstrate it better... (Goddamnit, there need to be a device that can dump mental images into PNGs on a PC. Get to work neuroscientists!) A close approximation to my idea was reached already with the quills on the werehog model in Sonic Unleashed, but it's still a bit off the mark.
The last thing on my list is perhaps more farfetched, but I'd like to see the removal of the "Spaghetti-arms/Legs". I'm not sure about the games, but I know for a fact that in SatAM and the Archie comics, the canon states that Mobians are partly human in their genetic code thanks to the Xorda's Gene-Bomb. If the new Sonic Boom designs are intending to reflect a partly human nature, they're starting to get somewhere... But the limbs still leave something to be desired. I personally would like to see something like this:
And:
Phew... enough of my rambling on for now. I'm mostly just a combination of tired, bored, and frustrated right now, and that tends to lead to long trains of thought.