I have never expressed this before, so don't expect a polished statement!
As there are so many religions in the world, this is a daunting task!
In India alone there are apparently over 300,000 religions.
Of the major 9 religions, one needs to study hard, and ignore clear differences, to find points that they have in common.
On the whole, most religions are a means of escaping from the reality of a rather unpleasant life for most people.
The biggest problem that I find with many religions is the rejection of life on earth combined with a hope for something better after death. This sort of belief is frequently combined with a denial of many of the good things related to physical life. Respect for other humans is not very high on the agenda of some religions. Most religions (or rather their followers) do not seem to condemn slavery, exploitation or cruelty and women have been suppressed by most religions for most of their history.
Each being, including humans, need certain basic conditions, food, water, fresh air , exercise etc. Surely one needs no religious beliefs to accept this. Perhaps this simple idea should be incorporated in all religious beliefs.
The Theosophical Society, founded in 1975, seems to have done most to find ideas in common with various religions. Most of their followers are vegetarian, mainly through respect for all life.
This is a linkhttp://en.wikipedia.org/wiki/Theosophy