I have to ask, which band started in the 80's, then went 90's?  Which version did you like better, and why?

Well, technically Nirvana started out 80's.  Just barely though, I think the first album was in 1988 or '89.  But they obviously didn't hit it big until 1991.

Bon Jovi still had some decent staying power in the 90's.  

Nirvana played there first show in April of 1988, so yea they started as an 80's band but certainly didn't sound it. There first album was Bleach released in June of 1989.

U2 was a solid band but burned out in the mid 90's, now they've come back strong.

Guns & Roses also came into the 90's with a full head of steam but fizzled out quickly, Nirvana kicked their ass.

The Beastie Boys and REM were around/popular during the 80s & '90s.

I was going to mention REM, APS :)

I think I prefer 90s REM. I do like some of their 80s stuff, but in my opinion, their better stuff was released in the 90s. Fpr example, 'Losing My Religion', 'Man on the Moon', 'What's The Frequency Kenneth', 'Daysleeper', 'Sidewinder Sleeps Tonight', 'Nightswimming', 'Strange Currencies', and the list goes on :)

Are we just mentioning bands, beacuse many soloists have crossed over successfully also?

- Madonna (prefer 80s in general, but she did put out some good stuff in the 90s too)
- Whitney Houston
- George Michael
...etc...

Crowded house
Erasure
Pet shop boys
Wet Wet Wet
New kids on the block (just about)
U2
UB40

Michael Jackson's last above average/good album, "Dangerous" was released in 1991.  

Actually Jackson did have a few decent hits with "HIStory" in 1995, but '91's "Dangerous" was the last album that he had that I liked.

Let's add:

New Order
The Beautiful South

Janet Jackson was popular in the 80s and 90s.
LL Cool J kept it up
in a way, you could say New Edition, they did have a hit in 1996, and in the early 90's the guys all had top 10 hits.

I think the question being asked here is which bands from the 80s changed their sound to keep up with the 90s?

Definitely U2, who added electronic influences into their sound. Much of their 90s work doesn't sound anything like the stuff they were doing in the 80s.

Motley Crue tried to stay relevant by changing their sound on 'Generation Swine' in the mid-90s but it didn't work.

There's other examples, but those are two I can think of.

Metallica changed their sound pretty significantly from one decade to the next.

The Cure and INXS went 90's. I remember in 97 INXS had a minor hit with "Elegantly Wasted". The Cure had a hit in 92 with "Friday I'm In Love". Gloria Estefan hit it big in the mid to late 80's but in the 90's had a hig hit with "Coming Out of The Dark" in 1991 and remade the late 70's disco classic "Turn The Beat Around in 94, also remade Carl Carlton's 70's hit "Everlasting Love" which was a Top 30 hit in 95. 80's New Wave band Human League had a hit in the 90's with "Tell Me When". Lionel Richie was huge in the 80's though had a hit in 92 with "Do It To Me One More Time" and 96 scored a minor hit with "Don't Want Lose You".  late 80's Pop/R&b artist Taylor Dayne remade Barry White's classic "Can't Get Enough Of Your Love" which was a hit in 93 and had a hit the same year with "Send Me a Lover". Somebody mentioned New Edition before they had a hit in 96 with "Hit Me Off". How can we forget about R&B artist Keith Sweat?  Hit it big in the 80's with "I Want Her" in 87 and scored a couple hits in 96 with "Twisted" and "Ain't Nobody".

Well, there's The Offspring!  their self titled album was first released in 1989 and then re-released in 1995. (I have the '95 version, which I think is cooler because it has Dexter Holland's record label on it)

They're still goin... I've read it's the last album for Columbia Records. And yes I know Ron Welty left the band to join a newer band.  I know a bunch about this band, being one of my most favorite bands in the world. I'm eager for "Chinese Democracy" to come out! Any other Offspring fans over here?

Madonna completely changed her image in 1989 so the transition into the 90s was always going to feature a different Madonna. I preferred the 80s Madonna myself and lost interest in her music after her Like A Prayer album

U2 were fantastic in the 80s and then faded quite badly in the 90s and 00s. I prefer their early 80s stuff, for me they also faded in the late 90s as they also changed. I love the earlier albums like War, Pride and The Joshua Tree

Michael Jackson was never my favourite artist but I feel he weathered the transition from 80s to 90s best. I prefer his early classics like Thriller and Billie Jean

Pet Shop Boys sucked after 1990 and I like very little of their later stuff. Please, Actually and Introspective feature all their best music

Human League made a comeback in the 90s and I liked their 80s and 90s music. They achieved nowhere near the status they held in the 80s though

I would say quite a few of the other artists mentioned weren't really established 80s artists - I think it is hard to compare an artist's transition from 80s to 90s unless they were truly established in the 80s and had (nearly) as much impact in the 90s

I guess Madonna wanted to get away from her 80s image but she produced some great songs in her early career like True Blue, Who's That Girl and Into The Groove. The films Desperately Seeking Susan and Who's That Girl didn't help her image much either (though I quite like both films)

Metallica really did some new things in the 90's, as well as they are these days.

I have to agree on the Metallica choice.  If you say their sound hasn't changed, you've lost some hearing listening to them.  Def Leppard has 'altered', but i wouldn't say they've change all the way.

And how about No Doubt?  Granted, most of their early stuff you have to dig REAL deep to find, but they have changed.  Then again, they seem to be in a constant state of flux anyway.  And that's just within an album!

SexArt (80's) then it changed some band members then got some new ones to KoRn was born! then they did there shows finally got a sign on i think in 1994 if i am right

Depeche Mode reinvented themselves for the 90's. They stopped being so synthpoppy, and started implementing guitars more into their music, without really becoming a rock band. They've experimented with different sounds and different styles, but still stayed primarily electronic. Just a little more modernised.

And commenting on something Criz had said about R.E.M.: I, personally, loved their music in the 80's! My favourite album is most probably Reckoning (1984), and I think they sounded great back then. This is not to say that they didn't sound great in the 90's though! I didn't like Out of Time at all, but Automatic For The People is another one of my favourite R.E.M. records...and they're still putting out great stuff today!

Absolutely Vile

Let's not forget Cher, the queen of re-invention, who went from 80's stuff like 'Just Like Jesse James' to 90's stuff like 'If I Could Turn Back Time' and 'Believe'.

Michael Jackson went 90's.


Howard

The Replacements and probably about 100 others, but can't think of em ???

Duran Duran of course was a huge 80s band who have also released songs in the 90s that were successful, even though the line up of Duran was different.  

The songs that Duran released in the 90s that made the most waves were "ordinary World", "Come Undone" which is one of my favorite Duran songs along with " Electric Barbarella"

Some seem to think that Ordinary world is an 80s song but they are mistaken. It was released in 93.

Rio

Duran Duran

The Cult was an 80's band that came into the 90's with "Sonic Temple" and "Ceremony". Their album "Beyond Good and Evil"rocks too.

Ministry - they dropped the synth/pop sound they started out with in the 80's and added some very heavy industrial sized guitars.

Nine Inch Nails - Trent also added aggressive guitar to the mix in the 90's.