I am a big monster girl fanatic. Monster Girls Unlimited used to be the central forum for Kenkou Cross' Monster Girl Encyclopedia stuff, but after making some dumb mistakes (I am a member), Kenkou Cross got a bad idea of Westerners. After some talking with a Westerner who ran a smaller MGE forum called Monster Girls Redux, he got on good terms and actually made it so that MGU couldn't host his stuff by sending a cease and desist to them after a rather ugly debacle.
Monster Girl Quest is a great game. Even excluding the porn stuff, it had a good story and memorable characters in my opinion. Of course, the sex with the characters make it more memorable. There are some flaws in the game, but nothing that's too denting to the overall fun.
I am eagerly awaiting the full release of Part 1 of the RPG Maker game Monster Girl Quest: Paradox. It's more of an RPG style take on MGQ, with an alternate timeline and all new enemies. You can even recruit monsters to work with you, feeding them (and diddling them) to get them to like you more. You can even choose who to work with at the bat; a sealed, loli Alice XVI, or a sealed, loli Ilias (who makes funny commentary on the monsters from what I hear). You can even recruit foes from MGQ like Promestein. Funnily enough in the demo, one of the strongest monsters you can encounter is Rami... the Imp from MGQ.
Another fun series is the Violated Hero series. I haven't played them all, but I love what I have played. 2 has plenty of unique girls, like the futa Hellhound Tama who loves (trying) to breed cute boys, Marybelle the post-partem Beelzebub who needs a man to carry her eggs. 3 has a little more... out-there bad ends, from a Scythe Weasel named Kirika who cuts you up while she gives you a footjob, to Purane, a rose alraune who has thorns inside her pussy. It has some bad ends which definitely aren't for everybody in the series, but if you love monster girls, chances are there's a girl you'll like (if only somewhat) in the series.
Everyday Monster Girl is a great series. It's got plenty of laughs while still mixing in some seriousness and a good plot. Being from the same guy who created some similar, more hentai comics a while back, there's plenty of ecchi stuff involved (shrinking a 'villain' by suckling her bosom), but if you want to have some laughs and love MGs, it's hard to go wrong.