Need some advice please. I trust my local CEGers more

Quite for some time I been having this weird problem with my car. Whenever I wouldn't drive it for over 24 hours, the battery's charge would drop to like 10/11V and the car wouldn't start unless a charger or booster cables were used. Then the car would start within a split second and would start/drive for another several months with full 12V (or 14V while running).

Now, 2 days ago I stayed home and forgot to drive it. Well, I am thinking - in the worst case scenario I will just throw some booster cables. That's what I did. So this immediately gave me 14V with stereo blastin' and all. However all I got was a measley click, no revvin' or nothing. I could have thought the alt went bad, but it doesn't look so - when it (alt went bad) happened in the past, the car would just go nuts with crazy blades movements, blinking/dimmin' of the cluster and all.

Then I tried to start it remotely with my Viper - the same effect/no effect.

What could be the problem? A starter?

Thanks,

RG