If you are running this game on a laptop with an NVidia graphics card, the NVidia cards aren't detected, and the configuration utility defaults to integrated Intel graphics which runs extremely slowly. To get game to work, see the Steam support forums on how to manually edit the config file so graphics card is detected and game then runs OK.

I dont think Amazon allows URL's so I'll copy what worked for me:

"...---- -OR USE THIS METHOD:- ----

TESTED WITH A GeForce GT 555M chip.

1) Open the NVIDIA Control Panel, go to "Manage 3D Settings" then "Program Settings". Add the sonicgenerations.exe executable and set the preferred graphics processor to be the NVIDIA one.

2) Open "Control Panel" and look for the "Device Manager". Open it and expand the "Display Adapters" item. Make a note of the exact name given to your NVIDIA adapter (including the use of capitalisation.

3) Use the Sonic Generations configuration tool to configure the game to your liking and save.

4) Go to the Sonic Generations directory (in most cases "C:\Program Files (x86)\Steam\steamapps\common\sonic generations") and open GraphicsConfig.cfg in notepad or your preferred text editing software.

5) You should notice that the second line will be the name of your Intel adapter. Replace this with the name of your NVIDIA adapter exactly as it appeared in Device Manager.

6) You should see a line that says something like "MONITOR\LGD0292\{4d36e96e-e325-11ce-bfc1-08002be10318}\ 0000" (this will vary depending on your exact setup, just look for line of this format), it should be the second to last line. Delete the contents of this line completely so you are left with a blank line. Here is my configuration file as an example:

Quote:
Do not manually edit this file, use the configuration tool.
NVIDIA GeForce GT 555M
\\.\DISPLAY1
1600.900.60
1
1
1
1
0
d7b78e66-4256-11cf-fd56-b424b7c2c535

1515474505

7) You should now be able to play the game

One thing that should be noted is that the line "\\.\DISPLAY1" may need changing as well. In my case, DISPLAY1 is fine when only my laptop display is enabled. However when the display was extended onto the "fake" Intel VGA display, I needed to change it to DISPLAY2. Therefore if DISPLAY1 does not work, I recommend trying DISPLAYi where i is the number of displays you currently have enabled.

NOTES: make sure you go to device manager and copy it exactly as it says(i had 5 spaces after GTX 580M for my card)

This second method was suggested by: ezodagrom. Thank you!"