People are always so good about sharing favorites in this forum, I thought I'd suggest people sharing older series that newer readers may have missed.  My contributions are:  2176 and Crimson City, two series while hard to find are IMHO well worth the seach.  They are a mix of paranormal and sci-fi elements but still worth a look.  They are introductions to earlier works of some of today's popular paranormal authors.  Happy reading!

9780505526229    Crimson City            Crimson City-1    Maverick Liz
9780505526328    A Taste Of Crimson    Crimson City-2    Liu Marjorie M
9780505526472    Through A Crimson Veil    Crimson City-3    O'Shea Patti   
9780505526588    A Darker Crimson    Crimson City-4    Jewel Carolyn   
9780505526724    Seduced By Crimson    Crimson City-5    Lee Jade
9780505526250    Crimson Rogue            Crimson City-6    Maverick Liz
9780505527103    Shards Of Crimson    Crimson City-7    (all)

9780505525420    The Legend Of Banzai Maguire    2176-1    Grant Susan
9780505525918    Day Of Fire                     2176-2    Nance Kathleen
9780505525895    The Shadow Runners            2176-3    Maverick Liz
9780505525932    The Power Of Two    2176-4    O'Shea Patti
9780505525970    The Scarlet Empress    2176-5    Grant Susan

Good Idea!

I'm currently reading the below series, and probably wouldn't have picked it up if a friend hadn't pretty much shoved it into my hands, lol.

Nancy A Collins - Sonja Blue Chronicles

1. Sunglasses After Dark
2. In the Blood
3. Paint it Black
4. A Dozen Black Roses
5. Darkest Heart

These are more of a dark fantasy, but well worth the read.  If you can't handle gore and violence, then these are not for you.

Stephen Dedman 

The Art of Arrow Cutting

Shadows Bite

SD's do not have romance in them.  Lean more towards horror.  But I keep rereading them. 

Donna Boyd

The Passion and The Promise

These aren't talked about much either, but they are pretty good.

By Deidre Knight

Midnight Warriors
1. Parallel Attraction (2006)
2. Parallel Heat (2006)
3. Parallel Seduction (2007)
4. Parallel Desire (2007)

One series I don't see mentioned here, that I am currently enjoying is the Immortals series by Jennifer Ashley, Robin T. Popp, and Joy Nash.

http://www.immortals-series.com/index2.html

Rosemary Edghill's series.  The Bast mystery series which starts with Speak Daggers to Her.

And the Elf series about the Twelve Treasures starting with The Sword of Maiden's Tears.

Tanya Huff's Blood series.  Looks like most of them are available.  They were reissued when the cable TV show was on.

Emma Bull's War of the Oaks.  One of the first of the urban fantasy books.  Very dated clothing. 

Really older series that I have re-read is a sci-fi futuristic romance series by Marilyn Campbell.

She was a terrific writer in the 80's-90's but she doesn't write fiction anymore.  :(

She wrote a series called 'innerworld' about a whole society of futuristic  characters w/ psychic abilities.

Some are hard to find but imho, well worth it.

I actually have a listmania list of older paranormals,  which are really more futuristic sci-fi romance, and time travels.

These were very popular before vamps and werewolves.   lol

Also loved Justine Davis.  The Skypirate is still one of my very very fav sci-fi romances.

Link to the listmania.   :)

http://www.amazon.com/Older-Paranormal-Romances-that-are-still-great/lm/R1HNNTUHNAWC2Z/ref=cm_lm_byauthor_title_full

Justine Davis also wrote under another name.  Justine Dare.  Still have several of her books.

Very old is also Zenna Henderson.  She wrote a series about a family with special abilities.  And there was a focus on the teacher.

Combining sci-fi, romance, and vampire-like people, Lorrah & Lichtenberg created a unique world where all people are NOT created equal.  "In Earth's far future, humanity mutates into two races.  The Gens generate a life-giving force.  The vampiric Simes need that force to survive."  At one time the taking of that force was brutal and always fatal.  But would love allow for a different way to be created?

First Channel                Lichtenberg, J; Lorrah, Jean        1980-12
Channel's Destiny       Lorrah, Jean                                    1983-12
Rensime                       Lichtenberg, Jacqueline                1984-01
House of Zeor              Lichtenberg, Jacqueline                1985-05
Unto Zeor Forever       Lichtenberg, Jacqueline                1985-09
Ambrov Keon                Lorrah, Jean                                    1986-02
Mahogany Trinrose     Lichtenberg, Jacqueline                1986-07
Zelerod's Doom           Lichtenberg, Jacqueline                1986-08

(Here's another one more strictly paranormal romance)  Rosemary Laurey wrote The Vampire Series

Kiss Me Forever/Love Me Forever (The Vampire Series, Books 1 & 2)   9780821776612

Tea with the Black Dragon by R A MacAvoy. 

Nayda (and another werewolf one?) by Pat Murphy.   And her SF book, The City, Not Long After, has a shifter. (Brilliant book. Recommend highly.)