A titles are "Awesome", they're the ones that are the most fun to play and have the deeper rule sets.
B titles are "Boring".

A title. Keeps you coming back as you are always finding new things and challenges in the game.
B title. Fun at first but you find that you are doing the same thing over and over again, nothing new to see and do.

However it really is in the eye of the beholder.
Just today I spoke to a guy who told me how much he loved Last Action Hero and would never part with it.
I couldn't see it myself, I've played the game but it doesn't really do anything for me.
I had a friend come over (not a pin head like most of my mates) and we had a few games.
He says
"Which game are you the best at?"
I say
"Getaway!"
I explain the rules to him whilst playing and he says
"Is that it!"
It's not a deep game but it is a lot of fun.

Everyone tells me Medieval Madness is one of the greatest game ever.  Yeah....... I don't think so.
One of the most over rated and over priced games out there.
It's a good game, just not that good.