I'd highly recommend Magiranger, Gekiranger, and Shinkenger. All three are very solid overall, especially Shinkenger.

id say

Shinkenger
Hurricanger*
Abaranger*
Gekiranger
Boukenger
Go-Onger
Dairanger*
Gingaman*
Timeranger*
Gaoranger

id say skip Carranger honestly the whole show was meant as a parody of sorts of Sentai and really its not that great. id say skip Magi and Deka as well as I find both of those unbelievably boring

and for the love of justice, just skip Goseiger you wont regret it

*= hard to find fully subbed & good quality

Chronologically:
Liveman
Jetman
Zyuranger
Dairanger
Kakuranger
Carranger
Megaranger
Timeranger
Hurricanger
Dekaranger
Gekiranger
Go-onger
Shinkenger
Gokaiger

I grew up watching Choudenshi Bioman, which is undoubtedly one of the best from the Showa era. I lost interest in Super Sentai when Power Rangers showed up. Then in 2004, I got hooked on Tokusou Sentai Dekaranger. At the same time, I picked up Denji Sentai Megaranger and Mirai Sentai Timeranger. I went offline on Super Sentai afterwards, but fully regained interest with Kaizoku Sentai Gokaiger, which had me downloading every Super Sentai series available online.

With that in mind, here are my recommendations:

Showa Era
Himitsu Sentai Goranger (1975)
Taiyo Sentai Sun Vulcan (1981)
Choudenshi Bioman (1984)
Choushinsei Flashman (1986)
Choujuu Sentai Liveman (1988)

Heisei Era
Choujin Sentai Jetman (1991)
Gosei Sentai Dairanger (1993)
Denji Sentai Megaranger (1997)
Mirai Sentai Timeranger (2000)
Hyakujuu Sentai Gaoranger (2001)
Tokusou Sentai Dekaranger (2004)
Jyuken Sentai Gekiranger (2007)
Samurai Sentai Shinkenger (2009)
Kaizoku Sentai Gokaiger (2011)

I'd recommend Go-onger only on the grounds that you're looking for something completely absurd and gimmicky.

I'll have to disagree with you on Gekiranger. It was pretty good yes, but it had a few glaring flaws. The introduction of Chopper was out of the blue. There was no build up or any kind of foreshadowing.

The only character in shinkenger that is not like any other in past sentai, for reds, is Shinken Red. The rest are generic character types.

Or if you want a more light hearted series with a fun cast of heroes and villains.

Hyakujuu Sentai Gaoranger was pretty good overall. It was the second Sentai I watched after Shinkenger. So it was cool is see an "older" series.