I don't know if I'm for the idea that "all religions lead to the same place". There just have to be some religions bad enough out there that can be excluded from the "good religions" category, and therefore should be place in the "bad religions" category.
What would be the standard of the "good" category. Good religions tend to have abstract ideologies (which is fine and good). Good religions must also have some guidelines for putting these ideologies into practice. Here are some possibilities (admittedly expressed in Christian terms):
1. Love God - Having some kind of focus on the importance of loving God and worship. Some kind of clarification that worship is a discipline as well as being enjoyable. That act of worship necessitates the believer to receive love from God
2. Love your neighbor - It would have to have some version of The Golden Rule as even atheists agree (Sam Harris, Karen Armstrong) this is the highest form of moral development.
3. Love is the "most excellent way" - The more stuff you do where love is the motivating principle the better. i.e., NOT giving the guy on the corner a dollar if you know he's going to buy crack. Again, this is a discipline as well as something that feels good.
4. Love you enemies - This is probably the truest litmus test as far as practice goes. My personal opinion is that if a religion teaches that someone should be killed or their rights limited because they believe the wrong stuff or the religion identifies their lifestyle as sinful, than this religion fails this test. On an even more practical level is the daily discipline of this guideline. Who will I come into contact today that I must love? Who did I fail to love yesterday and how can I learn from that mistake?