The first season has to be one of the worst cartoons ever made, though I'd rank the first season of the 90s FF cartoon below it.
The second season of both of those, however, are great.
The first season of
Iron Man was bad because:
*There was no recurrent theme or arc. It seemed like episodes always involved Tony Stark having a new invention that the Mandarin wanted, Iron Man and Force Works soon intervene against Mandarin's goons, and the day is saved. It felt like a reprisal of
Super Friends,
Masters of the Universe or any other '80s era action figured geared cartoon. It looked especially bad because at the same time,
X-Men over on Fox was able to appeal to both kids and adults.
*Virtually no character development. We have virtually little insight about Tony Stark's genius or his personal demons (outside of the two part "Origin of Iron Man" episode). In fact, the idea that Tony's Iron Man suit is like a life support system is pretty much nonexistent. Also, we don't really know anything about Force Works (other than they're around to sell more toys and provide Iron Man with backup against the Mandarin and company), why they work with Tony and how they came to be. Also, why is Justin Hammer (an evil mastermind in his own right) working with the Mandarin, other than they both dislike Iron Man?
*The animation (provided by a Canadian company called Rainbow Animation Group) left a lot to be desired. In order to save costs, stock footage was routinely used. Also, the primitive CGI sequence of Tony Stark putting his armor on was extremely out of place (it was basically an attempt to display something "cool" to the little kids watching) and oft-putting.
*The voice acting could be very inconsistent. For example, there are occasions in which War Machine's voice goes back and forth to being provided by James Avery and Jim Cummings (who otherwise provided the voice of MODOK). Scarlet Witch talks like Arianna Huffington, Hypnotia talks like a breathless bimbo, Mandarin talks like a cliched, maniacal madman, it just seemed very unpolished most of the time.
*The writing at times, even for a comic book based cartoon makes little sense. For example, in one episode, Iron Man is able to recharge his suit to full power just with the aid of small tape player.