Perfection

Tomoyo is commonly given the 'perfect' label - that she is the perfect character, the perfect companion. Tomoyo is either criticized or loved for her 'perfection'. Critisized because being flawless is boring and unrealistic - her character isn't genuine and you can't relate to her. Loved because Tomoyo is so inspirational.

Tomoyo is always right

Tomoyo will never ever make a mistake when 'reading' people. In fact, Tomoyo commonly knows others better than they know themselves. Tomoyo is always always right about what action other should take and will nudge them in the right direction.

Tomoyo can do no wrong

By 'wrong' I mean something morally wrong. Tomoyo is portrayed as someone who will never ever depart from what is right no matter the circumstance. Tomoyo is someone who will stand by her principles.

Tomoyo is 100% selfless

Tomoyo is always acting in a way that aids other's happiness. She will put others before herself. Sometimes, Tomoyo acts against her own interests for others' happiness (I'm talking about Sakura and Syaoran here).

Tomoyo is kind to everyone

Tomoyo is friendly and nice to everyone, even if they are being a bit of an idiot (i.e. Syaoran near the beginning of the series). Such a tolerance is incredible. Nothing seems to annoy or anger Tomoyo.

Conclusion

Tomoyo is an ideal. She has a heart that is 100% goodness. I don't think it's possible to be as selfless, kind and mature as she. I'm all for worshipping genuine characters but I adore Tomoyo just as much because she is something to strive for. True, no one in real life can reach the standard that is Tomoyo but we can still see how far we can go. You might ask 'Why bother to try at all because it's just impossible?' My answer for you is to imagine just how the world would be if nobody tried at all to be a 'good person'.