My rating scale:
5.0- All around excellent series and some aspect of it goes above and beyond every other anime that I have seen. Amazing.
4.5- Very good series, it can either not have the wow factor that pushes it above and beyond to get the 5/5 or it might have that factor but also have a few flaws that drag it down slightly. Excellent.
4.0- Generally enjoyable to watch from beginning to end but doesn't stand out as amazing. Above Average.
3.5- Usually an anime with some good ideas but a bit lacking in execution or an anime that doesn't do anything special but is well polished. Average.
3.0- Anime with a few redeeming qualities but not good enough to make me want to watch the next episode. Below Average
2.5- Some aspects of the series are average, but overall it often feels like a chore to watch. Failure
2.0 or less- How and why did I even make it through this trash?