Darth Pope said:
The first DMC has vastly inferior production values compared to DMC 3. Additionally the originals gameplay mechanics are clunky compared to DMC 3. On top of that DMC 3 has a superior story.
And I agree with you whole-heartedly. Even 3's ending was vastly superior to 1's, though I still prefer 1's credits.
However, I find that the original is still the best in the series, and it is for reasons that I will outline shortly. I'm not trying to change your mind on the matter. I just want you to see where I'm coming from, so bear with me.
First, the level design is so much more creative in the original. The castle was remarkable, the forest was spooky (ish), the pirate ship was, well, abominable, but no water level is ever good, and Hell lives up to its name design-wise by being horrifying (in a good way). Most of the environments in 1 were fascinating to look at, and the atmosphere of the game was and still is remarkable. 3 had no such atmosphere. Most of the environments were boring and monotonous, though I must admit that Hell's entrance was beautifully designed.
Second, I find that 1 had much better enemy designs than the other games overall. In 3, if it wasn't carrying a scythe, it was either badly designed, annoying to fight (not fun and challenging like it damn well should be), or both (usually both). They were just plain boring. Some of the bosses were cool, but the enemies were just plain uninspired.
The enemies of 1 were very diverse and interesting for the most part. The Beezlbubs can die in the deepest pits of hell and the Sargasso were a tad simple, but most of the other enemies were actually interesting on some level. From the shambling Marionettes with their arsenal of pain and the fucked up Sin Scissors/Scythes with their unnerving screams to the asshole semi-transparent Frosts and the screwed up, evil-laughing, surprisingly difficult Nobodies, the game had a variety of demons with differing strengths and weaknesses.
As far as bosses go, I'd say 1 and 3 are even on the design front.
Third, 3 had Vergil, while 1 had Nelo Angelo (same demon, delightfully different). I think I've made my point.
Fourth, while 3 had the largest arsenal of Devil Arms, there wasn't that much of a difference between all of them as far as combat-effectiveness goes, though Nevan is an exception, as it is pretty much all style and no usefulness. For the most part, weapons in 3 only served to make combat more stylish, and while this is far from being a bad thing, it isn't quite as good as what 1 did.
1 featured only two Devil Arms, Sparda excluded. Both were fun to use and stylish to watch. They were also designed in such a way that one weapon can completely outclass the other in varying situations. Style wasn't the only incentive in switching weapons.
Fifth, I find that the soundtrack in 1 is better than 3. I can't explain exactly why except to say that I just think that 1's music fit 1 better than 3's music fit 3.
All of the above is why I prefer 1 to the others. You get where I'm coming from, right?
EDIT: Oh wait. I forgot to mention the Devil Triggers. I liked how 1 approached it, sending strands of the weapon's element along his body, and when he attacked, his body transformed into the body of the demon for whom the weapon is named. In 3, they just made Dante look silly. Thank you, Kazuma Kaneko, for giving Dante butt-wings and a screwy looking head. And neck. And body. Pretty much a screwy looking everything.