Well despite being completely underwhelmed by the first Hajime no Ippo series, I decided to give New Challenger a shot largely for the sake of completism and I must admit that I was impressed. Nearly all of the major criticisms that I had of the first Hajime no Ippo don't exist in New Challenger.
Story: I complained that the original series was a copy paste-job for each new opponent with Ippo being an underdog, Ippo trains, Ippo starts to lose the fight early, he gets knocked down, he discovers his fighting spirit/guts, gets up and has a comeback KO. Well I am very pleased to say that this system is done away with in New Challenger. In fact they get about as far away from that story system that Ippo is actually in the ring in less than half of the fights in this series. The fights themselves are thrilling and, while not completely unpredictable, are at least far more individualized than in the first series.
I also whined about the romance and rival arcs being tossed to the curb in the first Hajime no Ippo, but New Challenger fixes that as well with Miyata actually gaining a role in events again and Kumi being given a few episodes focused on her. The other characters are also given more prominence in terms of back story and series focus.
The story also gets a plus for smoothly continuing from where Hajime no Ippo and the two OVAs left off and drawing connections and references to the previous installments. The comedic portions of the story are also far above the comedy in the first series and actually left me laughing out loud more than a few times.
What really knocked the story down a few points their bizarre way of ending the series...again. In Hajime no Ippo, the climactic final battle finishes at the end of the second to last episode, leaving the series finale as some random filler episode which really screwed the end-series catharsis that I normally experience. In New Challenger, the climactic battle finishes even earlier, half way through the second to last episode. The second half of that episode is spent on 10 minutes of horrible, groan-worthy puns by Manabu's family and Takamura (which seem even worse compared to the earlier comical sucess of the series).
The finale returns to the actual story, but it introduces three brand-new storylines. Why the writers decided to start three new arcs in the series finale is baffling. The only two reasons I can come up with is that they though the series would end after the 25th episode (which still doesn't explain what they were thinking with the second half of episode 25) or that this was a blatent attempt to force the audience to see the new season that is sure to be coming up. I can deal with cliffhangers or even introducing a new arc at the end of the finale, but to start a bunch of brand new arcs and go a full episode into them before abruptly cutting them off means they'll spend the first episode of the new season repeating all of the arcs for those who had forgotten which is just a waste of my time, so boooo!
Animation: Female character models still suck, such there was an effort to make the male character models better looking including giving Date Eiji a samurai-esq look and making Geromichi at least look interesting. The animation as a whole is crisper and neater than the original series, but that's to be expected as it's been 9 years since then. When New Challenger is stacked up against other 2009 animes, it falls short by a fair bit, especially with the backgrounds which don't seem to be much improved at all. Two specific visual points where I saw a massive improvement from the first series were the chacters' eyes (which are more vibrant and expressive) and the use of light (which makes the boxing matches almost a completely new experience). Again, the boxing matches are the big eye-candy draw of the series.
Sound: I loved the OP song. It was upbeat and fit the series perfectly. The ED song seemed like it should have belonged more in a romance anime ED, and that is only further enhanced by the images that accompany it. I enjoy the romance element of New Challenger, but I would have preferred an ED song more along the lines of the first series. Voice acting and sound effects (i.e. punching sounds) were well done again and I don't have a real criticism there.
Characters: This is another area where New Challenger fixed the problems of the first series. Opponent boxers no longer follow the revolving door policy of "you're fighting Ippo, that means you're worth following, oops you lost, now this anime doesn't acknowledge your existence anymore," although that may be more of a side effect of the widened scope of the boxing world (there are boxers other than Ippo out there 0.o) and the smaller episode count in New Challenger.
I also criticized Hajime no Ippo for having almost no character development and, again, New Challenger answers. We see Date Eiji change because of his championship match and we see Ippo and Takamura really mature throughout the series. They also let the rivalry between Ippo and Miyata develop instead of taking the first series' route of stuffing Miyata in a box and shipping him off to Thailand.
My least favorite character from the first series, Geromichi, makes a return, but I was actually happy about that as the writers gave him a completely revamped image and personality while giving sufficient explanation as for why the change happened. Aoki and Kimura don't develop much, but I can forgive that considering they were never forced into a situation that would demand them to change.
The series introduces three major new characters, Bryan Hawk, Ricardo Martinez, and Manabu. Martinez is the perfect image of a calm, veteran professional and will serve as a good contrast to Ippo's emotional style of boxing if Ippo ever manages to challenge him for the world title. Hawk is the reigning Jr. Middleweight world champ so he's Takamura's target for his title match. Hawk is a madman who apparently finds sexual gratification in boxing/violence and shows absolutely no respect towards anyone but he's actually been constructed pretty well to be a an enemy for whom the audience has no sympathy, but some pity. Manabu is the newcomer to the gym, but has no bearing on any of the story and has a shallow background at this point. It's clear that he was only introduced in preparation for the next season, so I can't really determine whether he's a good character or not yet.
Overall: Solid improvement on the core of the story from the first Hajime no Ippo series means that New Challenger is a must-see for all fans of the original series and could possibly be a reason why I would recommend others to this series. Good comedy, good cast, good development, and good variety equals a good anime.
Edited 10/7/10 slight overall score increase (7.8 to 8).