well it is in quran that allah will NOT forgive those who died on the path other than that of monotheism. you can debate in phlisophical terms about the mercy of allah, but quran is the criteria that Allah has revealed to us and we CAN judge using quran because that is allah's kalam.
Verily, those who disbelieve, and hinder (men) from the Path of Allâh (i.e. Islâm); then die while they are disbelievers, Allâh will not forgive them. (Muhammad 47:34)
Verily, Allâh forgives not that partners should be set up with him in worship, but He forgives except that (anything else) to whom He pleases, and whoever sets up partners with Allâh in worship, he has indeed invented a tremendous sin. (An-Nisa 4:48)
after this ayah is there any doubt that associating partners will NOT be forgiven, and that is a word of allah, so if we doubt that, we simply accuse allah of being stupid (naudubillah) because he cant make up his mind, some times he says he wont forgive polytheists, and then he says he might....
Verily! Allâh forgives not (the sin of) setting up partners in worship with Him, but He forgives whom he pleases sins other than that, and whoever sets up partners in worship with Allâh, has indeed strayed far away. (An-Nisa 4:116)
and secondly, we seem to have this feeling that if some one does good deeds by helping the needy or poor or whatever, he somehow 'deserves' jannah. but the point is that allah already has blessed us with so much blessings, such as life, ears, eyes, limbs, food, drinks, skin, shelter, comfort, and so on and on that our worships and charity even spanning our entire lives cant thank for those blessings let alone "earn" some thing to deserve anything in the here after.