Extra Controls:

Sonic and Knuckles(S&K) 1994
Sonic and Tails have defeated the Death Egg,
and it crashes on Angel Island again, just like them.
They see Knuckles coming out of a secret chamber, and decide
to investigate. The chamber holds a special stage ring.
When they walk to the ring, they are teleported to another chamber
that holds a large green emerald. An irate Knuckles
decides to interupt this discovery, and the trio get into
an argument. But while they're brawling,
who's watching Robotnik?...

Game Objective:

Extra Controls:

Knuckles Chaotix 1995
A new city has errupted on the Island. Robotnik has gone
to investigate it, and discovers
the Chaos Ring. By using the Ring, he can finally
get the Master Emerald. He sets up a base on the new city,
and has started freezing anyone that tried to
stop him. Some of these people are Mighty The Armadillio,
Charmy Bee, Vector the Crocodile, and almost Espio the Chameleon;
Knuckles managed to save him, and the pair
go off to save the rest of the Chaotix, and stop Robotnik's
plan.

Sonic 3D Flickies' Island 1996
Flicky Island is home to many mysterious Flicky Birds.
But Robotnik has decided to turn them
into robots, like he does with EVERY other animal.
Sonic has decided to take a trip to Flicky Island, and sees
the place in turmoil. He needs to free the birds and
grab the Chaos Emeralds before Robotnik does.

Sonic Jam(SJ) 1997
Sonic has evolved into 3D!!
Of course, Flicky Island was also 3D, but
that was at an angle. But, still...
Not much info about the story line, here.
But characters include Sonic, Knuckles, Tails and Dr Robotnik.

Sonic Adventure(SA) 1998
Dr Robotnik has freed Chaos, the liquid lifeform
that was in the Master Emerald for 3000 years.
This Chaos thing is some bad guy; he increases in size and
power with each Chaos Emerald he consumes, and
Dr Robotnik is feeding him the Emeralds! He soon forms
into Perfect Chaos, a huge monster that practically destroys
Station Square. It's up to Sonic, Knuckles, Tails, Amy, Big and
another mysterious echidna named Tikal to stop it.

Sonic Heroes(SH) 2004
Sonic Heroes is a completely different game altogther.
You control three characters at the same time,
each with their own abilities: 'Speed', 'Power and 'Fly'.
There are four teams with their own unique story line:
Team Sonic(Sonic Knuckles and Tails),
Team Dark(Shadow, Rouge, E-123 Omega),
Team Rose(Amy, Cream, Big) and Team Chaotix(Espio, Vector Charmy).
As you've probably guessed, Sonic, Espio, Shadow and Amy
use speed, Knuckles, Big, Omega and Vector use power,
and Tails, Rouge, Cream and Charmy use flight.
Each team's stories are as follows:-
Team Sonic:Tails and Knuckles find a note from
Robotnik, saying he's created the ultimate weapon,
and in three days he will conquer the world. They bring the
note to Sonic, who seems rather excited for
another adventure. They run off into the distance,
ready to defeat Robotnik.

In Team Chaotix' story, Vector and Espio are layzing around, when Charmy
flies in with a parcel, saying they have work.
Inside the parcel is a walkie-talkie, the speaker
on the other side says that he needs their help.
Espio thinks it's a rather dodgy situation,
but Vector and Charmy are too hyped up about the promise
of big pay. They decide to go on their mission, anyhow.