It depends on the game. I insist on having autosaves in any case. Some people are anal about auto saves. I never understood this. If you don't want to rely on autosaves then just do what you'd otherwise do and spam the quicksave key. Autosaves are there as a convenient backup in case you need it. Some games are dumb about when they autosave but even then it's better to have it and not need it than need it and not have it.
I particularly like games that are designed such that they only ever autosave without the need for manual saves. Arkham Asylum/City and the Tomb Raider 2013 reboot are good examples. Sometimes it's just nice to not have to deal with saving at all. It's a pain.
I prefer a game that gives both options as there are times where i've had to drop the game immediately without saving so it's nice to know i've got something to come back to, but outside a few games that auto save every other minute the auto save only occurs at big moments so it's nice tobe able to manuallly save as and when i want to.
I appreciate auto save when it's there but I also constantly save manually even in an auto save game. I think I prefer auto save for the convenience, but having the option to reset is easier if saved manually.
The "why not both" meme is the best answer.
Just have a single save slot set for the auto save and all the rest of the save slots for manual saving. That's the best way so you have your manual saves but have the auto backup if you need it. Lots of 90's games did it this way and it worked really well.