Halo does have a lot going for it. While I can't speak well of the game play, due to personal taste, I do enjoy the story of Halo. The plot points are rather cliche, but that's hard to avoid nowadays. In their favor is the fact that Halo doesn't make humanity's superior innovative skills and high adaptability war winning points. The only reason the story ends on a somewhat high note is because the Covenant lose their greatest military asset: the Elites.
Annyyyyway....
Again, the Halo series has a lot going for it: popular game play, a good storyline, the best online console system to date behind it, and lots and lots of money to be poured in. The series has become wildly successful, breaking records left and right at the releases. Just about everywhere you go, people in the current generation will know Halo in some way or form.
And yet, Halo falls short where Star Wars succeeded spectacularly: cultural impact.
When Star Wars first came out, it premiered in 32 theaters across the U.S. It debuted a month before the main summer season, was expected to fail horribly, and (to my knowledge) was not exactly well known or anticipated.
By the end of its first year it smashed previous box office records; lines were forming around street corners for weeks, Mark Hamill, Carrie Fisher, and Harrison Ford went from relative unknowns to household names, and quotes from the movie were being spoken right and left. Even the guys who made the models and special affects were having kids ask them for autographs.
Thirty years later, and people still adore the series. Fans are willing to stomach the bad parts of the prequels to watch the few great scenes they had to offer (thank God for the DVD, and its ability to skip whole scenes). Whether openly saying "Luke, I am your father!" to having the main villain wear a face mask and Germanesque helmet, Star Wars pervades culture in the U.S. and around the world.
That's something that Halo simply has not achieved. Oh, I hear people talking about the fun they have playing Halo, I've seen Red vs. Blue, but still, Halo simply is no where near Star Wars. I don't routinely hear people saying "I need a weapon," or anything like that all the time. Outside of gamers, there is not much interest in Halo, something Star Wars doesn't have to worry about. Star Wars received universal praise; Halo took between five and six years to become really popular in Japan.
Not all of Halo's cultural shortcomings are due to any fault in the game. Much of what Star Wars became was about timing: movies were slumping in original material, America had recently lost the Vietnam War, the upheavals of the 60's and early 70's were starting to go bad. Halo, on the other hand, entered at the time when gaming was still revving up. Star Wars had a culturally unifying story, aimed specifically at the conventions of epic tales that one can find in any culture's mythology. Halo's story is a Hollywood cliche re imagined.
The Original Trilogy, at least, offered something new and exciting with each new movie. The movies all began within at least a year of each other, yet you can see from the beginning that the characters have grown and matured. In Halo, the only way you know the Master Chief has changed much is the new armor, and the subsequent dings and scratches (and Cortana's blatant self-consciousness; how many hair styles does she need?)
Even the tone of the movies changed: Episode IV had a good sense of classic, Flash Gordon good vs. evil to it. The Empire Strikes Back was much darker, with the heroes constantly on the run from the Galactic Empire (perhaps the most iconic image from the movie, for me, is the shot of the AT-AT's looming over the retreating Rebels). The movie at least ended with a ray of hope. Revenge-er.. Return of the Jedi finished with an excellent finality to it: you could tell this was the last battle (until the Expanded Universe realized that killing Thrawn meant that they had no more good villains, and had to make Vader's redemption next to pointless). Having played Halo and Halo 2, I felt a lot like I was just playing parts 1 and 2 of the same game. From the cutscenes I've scene, Halo 3 does manages to mix the darkness of ESB with the last battle tone of RotJ.
In the long run, Halo has the potential to overtake Star Wars in overall financial success (unless LucasArts pulls something far better than Knights of the Old Republic out of their hat...but I'm not holding my breath). However, it will never achieve what Star Wars did as a series, or as a cultural icon. Thirty years from now, I'll bet that people will still know the words "May the Force be with you," but I hold doubts for the Chief or Cortana getting that same recognition...