Ad-aware  6.0 build 181   Downloads  19,021,278

Spy Sweeper 2.1 ( New ) Downloads   594,264

SpyBot-S&D  1.2            Downloads 2,704.502

All three of these programs have 5 stars.

Which one of these programs is the best?          

I haven't tried Spy Sweeper but
I use both Ad Aware and Spy Bot together as neither is
perfect.  Each one seems to miss somehting the other catches.

As above :)

more than one is always better than just one alone.  another that i would consider is pest patrol.

i use ad-aware only :)

Spy Sweeper 2.1

Spy Sweeper detects and safely removes all forms of invasive spyware, including Trojans, adware, key loggers, and system monitors. New Version 2.1 features a real-time active memory shield, smart sweeper technology that adapts to dynamically changing spies to ensure your protection, support for detachable and network drives, customizable sweeping options to save you time and one-click access to a detailed spy database.

Why I need Spy Sweeper?

Spyware infects 9 out of 10 Internet connected PCs and has eclipsed viruses as the #1 threat to online privacy.
The consequences of unidentified spyware can include identity theft, computer corruption and bombardment from pop-up ads.
Spyware can easily bypass anti-virus and firewall protection by piggybacking on legitimate downloads to stealthily install on your system without your knowledge.
Spyware programs are deeply rooted applications that intertwine with core system functions to make manual removal without system disruption nearly impossible for most PC users.
hxxp://www.webroot.com/wb/products/spysweeper/index.php

I actually run all 3 programs on my system without
any problems, amongst all 3 you can be quite confident that they will
catch any nasty if it turns up ...

And they are all very easy to update too !!

PS

I also run Pest Patrol

You can't be safe enough :)

Being honest though Spy Sweeper has always been the one for me that has notified me when something has got into my system

Ad Aware is my spyware removing software of choice.  I should get another as well though as richardc2000 said, "no one is perfect".  But if you only have one, Ad Aware seems to be prefered by most and I have only good thinsg to say about it.

You won't need to be so reliant on spyware removers of you don't install things you don't need or don't know are spyware free  Beware the neat tools advertised to help you...always be skeptical.

I mainly use Adaware 6 but as a backup i always keep a copy of SpyBot-S&D handy

I use Adaware 6 build 181 and  SpyBot-S&D