I don't know about good trains because opinion differ among members here but I saw a list of top 10 bad trains by Ganga times in May last year. Most of them are bad due to late and some due to dirtiness.
1) Bhagalpur Anand vihar garib rath.
2) Padatik express.
3)...
more... Anand vihar Kolkata chitpur express.
4 ) Saharsa Amritsar garib rath.
5) New Delhi dibrugarh rajdhani.
6) Shri Mata Vaishno Devi bandra swaraj express.
7) Seemanchal express.
8) Tripura sundari express.
9) Manduadih rameswaram weekly express.
10) Himgiri super fast
Note - This is not a full list. We know that there are several trains out there which are bad but never made to this list.