It's been another week now, and I feel like I've made enough progress to start being more specific in my work. So, I thought I'd list the games I've worked on so far and what I've done with them.
Note that these are the settings I created for the Easy mode. I haven't started the Medium modes yet.
Castlevania 1 & 3: Doubled starting life, starting hearts, starting # of lives. Also, doubled recovery from recovery items and hearts
Journey to Silius: Doubled starting life, starting # of lives, starting weapon energy. Also, doubled recovery from recovery pellets, both life and energy
Ninja Gaiden 1, 2, 3: Doubled starting life & starting # of lives. Doubled recovery life from recovery items. Cut Spiritual Power consumption in half. In #3, doubled # of continues.
TMNT: Doubled starting life. Doubled amount of ammo regained from missiles, weapons, rope, and doubled life recovered from pizza. Doubled amount of damage done to enemies from attacks
TMNT 2: Doubled starting life & damage done to enemies.
TMNT 3: Cut energy consumption & damage taken from enemies in half. Doubled # of starting lives & # of continues.
I've also done a lot of work on the Double Dragon series, but haven't finished yet so I refrained from putting those games on this list.
I am still in the testing process and so am not ready to release anything yet. But, I am getting there. It is very true that all games are different. Each one seems to have its own way of doing things (many of which do not make any sense at all), and sometimes unexpected things happen. I've had to find and modify a lot of addresses in a few troublesome ones. But, I've also learned some tricks in the process.
I'll keep at this, so there will be more updates later.