Okay, I'm sure it's no small secret by now that Akira Toriyama originally intended to end the entire Dragonball story with the conclusion of the Freeza saga. Of course, the series was so popluar that he was more or less "forced" to work on it. Now let's think back to where the Z Warriors are at in the beginning of the Freeza saga.
Okay, they just fought off the Saiyans, Vegeta escapes badly wounded while Nappa is killed. The victory comes at a heavy cost as Yamcha, Tien, Chaozu and Piccolo have all died. With Piccolo dead and Kami by extension, the Dragonballs are gone. But having learned the origins of Goku and Piccolo as a Saiyan and a Namekian, they decide to journey to Planet Namek where the original Dragonballs reside so that they can bring all their friends back to life. Goku is too badly injured from his fight with Vegeta to go, so Gohan, Kuririn and Bulma go to Namek.
Now, we've had hints of somebody who's above Vegeta and Kaio (King Kai) remarks that even with Vegeta defeated, the "root of all evil is not extinguished" or something along those lines. And my friend claims that when Raditz tells Goku that he's needed to take over a planet, he thinks he's referring to Namek. I'm not sure if I agree with him, but whatever...
So, at the start of the Freeza saga, we find out Vegeta's boss is Freeza, who is said to be the most powerful being in the universe and it seems to show, he's an evil deity with a huge galatic empire under his command. So on Namek, we get a three-way chase for the Dragonballs, between Gohan, Kuririn and Bulma, Vegeta, and Freeza with Goku later on the way in his own spacecraft to help out. So we reach the point where Gohan and Kuririn are forced to team up with Vegeta, the lesser of the two evils in order to keep Freeza from getting his wish, but it seems as though Freeza holds all the cards and will come away as the winner until Goku shows up, more powerful than ever before and Vegeta is shocked that a "low-level" could've possibly become a "Super Saiyan". (Super Saiyans are foreshadowed when Freeza talks about having a premeniotion (sp?) of a Saiyan that would rise to challenge him. (In the anime, we see Goku sleeping as he's saying this, pretty much giving it away who the Saiyan is, if it weren't obvious already)
Also, we learn from the Great Elder, the reason the Dragonballs exist and that Kami came from the Dragon Clan of Namek and why Kami came to Earth, so here now Akira Toriyama has given pretty much the entire backstory of the series. We know now that Goku's a Saiyan, Freeza used to command the Saiyans until he decided to eliminate them out of fear of the "Super Saiyan" legend and we learn that the Dragonballs came from Namek and just why that is. In a sense, the story all started on Namek, and so it's coming to an end on Namek.
So the final battle with Freeza takes place and you get the sense that this is a culmination of the entire saga. Now as far as the original ending goes, I think it would've gone the same way minus the Mr. Popo finding the Earth Dragonballs and wishing all those killed by Freeza back to life so all those Nameks and Vegeta would probably stayed dead (There would be no big redemption story for Vegeta, he would've died essentially evil, but even so, with him pouring his heart out to Goku, it would've had a "What could've been if not for Freeza" moment) With Freeza pretty much responsible for the genocide of not one, but TWO races (Saiyans and Nameks) he is clearly meant to be seen as the ultimate evil in the Dragonball story.
With no Dende to heal him, Piccolo probably would've died as well due to the fact that he took a very severe injury and would've eventually died thus Kami would've died again and the Dragonball story would truly be over since well, the Dragonballs neither Earth nor Namek would no longer exist and Kuririn, Yamcha, Tien and Chaozu would've stayed dead.
Sounds like a real downer ending? Well, not entirely. There's the little matter of Goku, becoming a Super Saiyan. The "Legendary Warrior" who last appeared over 3000 years ago. Throughout the entire course of the series, we've watched Goku grow from a naive little boy who happened to be very strong into a grown man. And the irony, of course is, that he was denounced by the Saiyans as a "low-class warrior" and every single enemy in the series pretty much underestimated Goku and yet of all the Saiyans to become the legendary warrior, it was this low-level who rose above the bars that were set, overcame all the barriers and achieved something that no other Saiyan was able to do. All Saiyans dreamed of becoming a Super Saiyan (or at least deemed it as a legend) and we know all Saiyans were combat-angry and just loved to fight. (Something that Freeza played on to use them, I'm sure) And the one Saiyan who happens to be... you know, pure and good-hearted is the one to achieve the form of a Super Saiyan.
Now, Gohan and Bulma were to survive, I'm sure, but I've heard some conflicting reports that Goku was to die at the end, but that hasn't exactly been proven. (In my opinon, Goku should've escaped the same way he did in the original story) And then with everyone thinking that Goku beat Freeza at the cost of his own life, Gohan and Chichi are at their home, Gohan is studying while Chichi is making dinner for the two of them, they both get into a talk about Goku, when suddenly they hear something crashing outside, and hurriedly run out, and see a spacecraft on the ground, when out climbs Goku, alive after all and a happy reunion is had by all. ....well, that's how I would've done it if I was Toriyama and not told that I'd have to continue the story for yet another saga because it was so popular, feel free to call it cheesy or awesome if you want to. (It'd be awesome if Akira Toriyama ever made a special "What if" chapter with the ending he originally had in mind with the Freeza saga)
Now yes, most of the other heroes would be dead, but you know... they would've at least gone out fighting and not reduced to the background/useless characters they eventually became. We watched Goku train with Master Roshi, the then strongest fighter in the world, then Karin, Roshi's master, then Kami (God himself) and finally Kaio, the Lord of the Worlds, Goku has essentially trained with just about everyone, who else was there to train under? And having defeated Freeza, the most powerful warrior in the universe, Goku has now indeed become the strongest in the universe, therefore fufilling his desire to become the strongest. Goku's journey is complete in this sense and with the Dragonballs gone forever, this gives you the sense that the story is indeed truly over.
Now there are indeed some good things in the Cell and Buu sagas, but looking at it this way, I can understand why Toriyama wanted to end it with the Freeza saga, it would've ended the series with a sense of symbolism. Rather than the rather oen-ended conclusion to the Buu Saga which was probably forced upon him, due to Toei wanting to continue the series.
Anyway, that's just my thoughts. Feel free to discuss.