Just out of curiosity, what are your favorite bgame intro movies? This doesn’t mean the game itself is good: just that the opening video was REALLY cool in of itself and made you buy (or consider buying) it on that alone. As for me? Well just off the top of my head:
[list]Dies Irae
MinDeaD BlooD
Sabae No Ou[/list]
Any of the Sakura Taisen intros are fine too:
[list]Sakura Taisen 2
Sakura Taisen 5[/list]
Aside from MDB, GSS, and Gun Katana:
Cartagura
http://www.animepile.net/anime/Cartagra … Movie.html
Pianissimo
http://www.animepile.net/anime/_Innocen … ssimo.html
Hourglass of Summer
http://www.youtube.com/watch?v=15y13X34GW4
Yume Miru Kusuri
http://www.youtube.com/watch?v=FHBEbxCRQKU
Ever 17
http://www.youtube.com/watch?v=siOCjEydLUU
Tonarizuma
(you right click and save as to download the theme (sorry couldn’t find a video for the opening theme)
(on a note though, I’ve only played some of this game being a fan of the artist for it, but so far despite it’s good opening theme, I have not been able to enjoy it because it’s story just isn’t that interesting, and the ero scenes I’ve come across feel too long and drawn out (a difference from some games like MDB and GSS where the scene may be long but still good), maybe further scenarios will prove me wrong but for now I’ve decided to just put this on the backburner and play Gun Katana
http://mirror2.pachi.ac:8000/download/2 … _heart.mp3
Family Project
ef -the first tale-*
ef -the latter tale-*
Kaze no Uta‡
MuvLuv Alternative (either, they’re both good)¬Ü
Boku ga SADAME, Kimi ni wa tsubasa wo‡
Cartagra (the first one, mind, not the second or third)†
Pianissimo
CHAOS;HEAD
Tamayura (I liked this one so much I translated and subbed it =p)‡
Tamayura -Enkan no Kizuna- (note that all three Tamayura OPs come with Tamayura -Enkan no Kizuna-
Tamayura PS2
Kimi ga Nozomu Eien†
BITTERSWEET FOOLS
Touka Gettan‡
SWAN SONG†
kinda old but one game intro that leaves me a rather deep impression is giga’s baldrforce
YMK and Ever 17 whithout any hesitation.
But I almost only know OP of translated eroge.
Out of the ones people have already mentioned, Gore Screaming Show, Gun Katana, MinDead Blood and the two ef movies. I also like the Clannad OP and the Little Busters! OPs. (The LB Ecstasy OP has a better movie, but the remixed song is much worse than the original).
Another of my favourite OP’s is for Bazooka Cafe, as it really gives you a feel for what the characters and gameplay will be like, without worrying about any special effects.
I also like August intros because of the art and music.
Sad that I recognise so many of these Kotoko songs despite never having seen the OPs before. =p
EDIT:
I don’t know what this is, but I like it! Besides, there’s an upper limit to how bad a game can be with the ‘nitroplus’ name attached, so it can’t hurt to check it out.
Along with Satsuriku no Jango, I’d mention:
Jingai Makyou
(gratuitously awesome animation, great song)
Bullet Butlers
(great song, decent direction, great game)
Ane wa Erokomi Henshuusha
(poppy denpa madness, clever animation)
Harukani Aogi, Uruwashino
(melancholy, nostalgic song)
Kazoku Keikaku
(a Kotoko classic)
Shichinin no Online Gamers ~Offline~
(because I’m a Sano Toshihide fanboy, and the song is good)
That’s what I’ve got off the top of my head… will post more as they come to mind.
OMG!!! That bouncy-insanity reminds me of the Colorful series introductions… which reminds that they’re addictive too. 
[list]Colorful Kiss
Colorful Wish[/list]
Another favorite along those lines is the Kimihagu OP.
INO art? Check. Machine-gun talking polar bear? Check. MOSAIC.WAV denpa? Check. PENGUIN WARNING? Check. A nigh lethal combination!
Man, I completely forgot one OP I absolutely adore- the one for Liar-soft’s FOREST. It’s so… O_O
Here’s a youtube of it (dunno what the quality’s like, just found it through searching).
http://www.youtube.com/watch?v=U0KisohqXdk
The OP link on the website is dead, but holyseal still has it.
I like Kazoku Keikaku’s OP, but I specifically like the first one more. Too bad it only comes in 320x240, as far as I can tell. :<
I’ve too many favorite opening movies to count/remember, even my YouTube channel lists only a part of my wet dreams :oops: 
.
However, I buy my h-games ONLY after reading the reviews, because nice intros for crap games are frequent, unfortunately (the ONLY exceptions so far to my self-imposed rule have been the intros of Papikon and, to a lesser extent -i.e. I’ve specifically searched for the most cheapest copy on sale-, Kissing!! Under The Mistletoe).
For me… None
Simply because i found them to be lower or egal qualities of the Openning for under average/crappy Animes, so i don’t remember them at all… And anyway none of them could ever compet with my Favorite Game OP who can still give shivers and make my grin when i think of the pleasure and enjoyement i’ll get while playing it… Even if it’s a 8 years old DreamCast Game.
ToHeart2 and its parody ToHeart2 ~AnotherDays~, AYAKASHI, Shirotsume Souwa ~Episode of the Clovers~, Zanma Taisei Demonbane.
I usually enjoy OPs that are more than mere shows of the game CGs, and without the way too common presentation of the characters, with their names and all.
Gore Screaming Show is definitely my favorite.
I’m surprised though no one has mentioned “Brave Soul.” Maybe I’m missing something, but the entire thing is FULLY ANIMATED, as in no still-images (unless you count the map pics at the beginning). I’d love to see more hentai’s get full animation treatment, but instead it seems a lot of them cheat with still images of girls moved dynamically to simulate movement. I know, I know, animation costs time and money which is too burdensome for hentai developers, but that’s also why I think Brave Soul’s intro is awesome because they didn’t succumb to those restrictions.
I thought the music was excellent too:
Lots of titles have fully-animated openings.
Aka
Majipuri ~Wonder Cradle~
Utawarerumono
BITTERSWEET FOOLS
Haru no Ashioto
ef -the first tale-
ef -the latter tale-
Those are just ones that immediately come to mind. Unfortunately, the quality sometimes suffers a bit compared to the actual visuals, because it’s animated (although all the minori ones look beautiful anyway, thanks to Makoto Shinkai’s amazing work). Haru no Ashioto also had four fully-animated ENDINGS, one for each heroine.
Oh, forgot Utawarerumono indeed. Quite pleasant as well. As for “fully animated OPs”, that’s the case of all the ones I posted, save for Demonbane.
Of the games I posted, three have animated openings. ef and Haru no Ashioto were already mentioned, and the third is AshitaKimi.