Tyrion when he talks to Aegon tells him that Cersei is greedy for power, honor, and love. Cersei certainly wants power and wants honor in a sense that she wants to be honored, but love? Cersei has a Tywin like attitude toward love she only loves herself. Why would Tyrion think Cersei wants love?
For anyone looking up the quote, it's in Tyrion VI, ADWD.
Cersei was willing to risk everything to maintain her relationship with the sexual partner she chose. She defended Joffrey to the hilt and transferred a great deal of that feeling to Tommen - in AFFC Margaery devastatingly points out that Tommen will never have a wife Cersei doesn't hate (because that means Cersei won't be the central pillar of her son's world).
Cersei wants to be loved, not necessarily to love others. She doesn't want or see the need to be widely loved. We're not talking about anything healthy here. But she does want to be the focus of the love of the people she feels strongly about. She cannot have enough of Jaime's love or the love of her children. Indeed, she cannot cope with Jaime doing things like acting on his love for Tyrion or trying to do his job properly, because both those things lead Jaime to not privileging her desires over everything else.
And yes, Tyrion knows this about Cersei because a) he's known Cersei intimately for a long time and b) this is also what he's greedy for.
It's almost like their father left them a shared deficit in their emotional lives and neither have been able to sort through the damage...
