In addition to all of the real Sega games you can develop, there are a ton of hidden parody games. These include artwork very similar to the games they're referencing, usually with some kind of terrible pun. Some are obvious to English speakers ("Ace Wombat 2", "Mortal Wombat", "Final Pharmacy VIII"), while others require some Japanese to understand.
"Kaze no Klonoa" means "Klonoa of the Wind" (simply called "Klonoa" outside of Japan), but "kaze" also means "cold", as in the sickness. The Lupin game actually says "Chopin the 3rd", hence the composer motif. The Megaman one says "Rokujoman", a play on "Rockman" - "rokujo" is an arrangement of tatami mats. The Valkyrie Profile one reads "Valkyrie Frohaile". "Profile" in Japanese is pronounced "purofairu" - "Frohaile" is a mangling of the term "furo hairu", which means "to take a bath", which is why Lenneth is in a steam bath with a towel. The Fatal Fury one reads "Garou Dentetsu" - the Japanese name is "Garou Densetsu", while a "dentetsu" is a train - the picture shows Terry (or a Terry-a-like) wearing a train conductor uniform. The "Lolly" ones, for "Sega Lolly" and "Lolly X" are a variation on "loli", the term for little girls, usually in a sexual context, here used jokingly. The Metal Gear Solid one reads "Otalu Gear Solid" - "Otalu" should be "Otaru", a Japanese resort town.
"Daken X" is a play of Maken X, where "daken" is a slang term for a dog (more appropriately, mongrel.) The Tokimeki Memorial picture is blurred out because Konami was notorious for protecting its copyrights and preventing doujinshi authors from featuring their characters in their porn comics. The To Heart one reads "toohato", which means "ten pigeons", hence why Akari is surrounded by birds. The Ys one reads "Sauce", and surely enough, there's a bottle of sauce in between the goddess' hands. The one with the salad reads "E no Shokuji", a parody of "D no Shokuji" ("D's Diner"), known outside of Japan simply as D. The title and the blurred out face are Kenji Eno, a rather notorious game developer.