When you say 'types' what are you looking for, the basic groups currently within the genus? A list of species? Those currently popular or common in the hobby?
Listing (and learning) them all is a bit of a tall order, since there are many, and listing those within the current genus doesn't give you a complete picture, since there are also closely related or similar types and/or those formerly classified as Geophagus (like Gymnogeophagus, Satanoperca, Retroculus) and some that will likely be reclassified one day (Brasiliensis). And, yes, many of them look similar. Short of buying and studying the Thomas Weidner book (South American Eartheaters) for big $ (because it's out of print), there's not really a shortcut unless you just want a few basics. You'd basically need to invest some time learning about them if you wanted to get beyond basic groups, each of which includes several to numerous species and/or an as yet unclassified multitude of local variations.
Sample resources you could look at or that give you an idea what you're dealing with:
Profiles page
List of described species currently within the genus "Geophagus"
Images to browse and click to start finding more information
Otherwise, some basic groups currently within the genus would be Brasiliensis, Altifrons, steindachneri (and it's relatives) and Suriname types, which is a sort of general purpose bin into which a lot of the others have been tossed, which doesn't help identify species and doesn't necessarily mean they come from Suriname.