Even though Tupac Shakur was labeled the "James Dean of hip-hop" during the final turbulent years of his life, it seems the iconic rapper may have more in common with Elvis Presley.

Besides the fact that conspiracy-theorist fans of both artists believe their fallen heroes are still alive, Presley and 'Pac have become legendary in their respective genres, inspiring conferences and tributes — and enthralling fans with their music years after their deaths.

And now, a fourth posthumous Tupac album, the double disc Until the End of Time, arrives in stores on Tuesday, garnering the rapper/actor's work even more attention.

Tupac's first three albums after he was killed in Las Vegas in 1996 by unknown assailants — 1996's The Don Killuminati: The 7 Day Theory (under the name Makaveli), 1997's R U Still Down? (Remember Me) and 1999's Still I Rise (with the Outlawz) — have sold nearly 7 million copies, while the four albums he released while he was alive have sold 9 million. Add to that a triple-platinum greatest hits album released in 1998 and dozens of bootlegs of his material, not to mention assorted songs on various other releases, including Death Row Records' Too Gangsta for Radio. Another two-disc Tupac set is scheduled for release in November.

"Now that he's gone, people are embracing him more than ever because he was really saying something," says producer DJ Hi-Tek. "He's a real role model because of his strength and his I-don't-give-a-f--- attitude toward bullsh--. He died too early, right at his peak. That's why I feel people can't let him go."

Other rappers, such as the Notorious B.I.G., Big Punisher and Big L, have also had material released posthumously, but none of it has enjoyed the critical and commercial success of Tupac's posthumous releases.

Many industry insiders say that's because Tupac was seen as more than just a rapper.

"He was like a leader, not a rapper," said Trick Daddy, who is on the long list of rhymers accused of adopting Tupac's thug aesthetic. "He was like [Nation of Islam leader Louis] Farrakhan. People believed in what he said and they took it to heart. Other people just make music. Pac couldn't make a bad album, a bad song. Biggie was good too, but he [only] had good music. Pac was like a visionary."

Added Big Boy, a radio personality for Power 106 in Tupac's adopted hometown of Los Angeles: "Tupac was so far ahead of his time. I haven't heard the entire [Until the End of Time] album, but he is right on target about things happening today."

Tupac's vision, some feel, is what allows his music to remain relevant to hip-hop fans who choose new heroes almost as quickly as they choose which outfit they're going to wear to the club this weekend. Whereas many other popular rappers deal with material items that can change from season to season, Tupac tackled more personal, timeless issues: jealousy, pain, deceit, love, lust and rage.

"I'm not really into Nelly and Jay-Z because all they talk about is being rich," says Priscilla Ochoa, a Long Beach, California, resident who is a die-hard Tupac fan. "I can't identify with that. ... Tupac has songs that are about being a player, but a lot of his songs are about his life and what he went through, which is why I think people can relate to him."

It's also been much easier to relate to Tupac since his death because of the seemingly endless onslaught of new, good material from his estate. Unlike Biggie, whose second posthumous album, 1999's Born Again, and Big L, whose sole posthumous release, 2000's The Big Picture, featured previously released material from mix tapes, freestyles and B-sides, most of Tupac's posthumous material had never been released in any form. It is estimated that he left behind 150 unreleased songs when he died, far more than Biggie, Big L or Big Punisher, the latter of whom has a second posthumous album, Endangered Species, scheduled to arrive in stores April 3.

"Tupac was prolific from the time that he began writing, which was probably about 6 years old," said Tupac's mother, Afeni Shakur, who was an executive producer of Until the End of Time. As long as there are unreleased Tupac songs there will be more albums, she said.

"He didn't change and start to be prolific, change and start to be good. Before he was murdered, he did a lot with his time and his life."

Said Julio G, an on-air personality for Los Angeles radio station 100.3 "The Beat": "I've worked with rappers before and they don't record like that. When I listen to his stuff, I really, really analyze what he was writing before his death. He must have known what was going to happen because had he lived, there's no way all of that could have been released during his lifetime."

Since his death, however, much of the discussion surrounding Tupac has focused on his music, but Preston Holmes, a movie producer who worked with Tupac, said the medium wasn't even his strongest.

"I think he was an extremely talented person on a number of levels and he found several outlets to express himself," said Holmes, a co-producer of "Juice" and the executive producer of "Gridlock'd," two of Tupac's most critically acclaimed roles.

"I think his poetry gives a more accurate picture of who he is than anything else that he did," Holmes said. "When you're performing, you somewhat become what the audience wants, but when you're writing poetry, it's more of one-on-one conversations with yourself."

As far as his musical legacy, it's clear that Tupac and his works — all of them — will continue to resonate.

" 'Pac was a strong influence on the game," said Bone Thugs-N-Harmony's Krayzie Bone, whose group featured Tupac on its 1997 album, The Art of War. "He brought excitement and was the type of artist that always had you wondering what he was going to do next. I know that I buy every album that comes out."