Both games have pros and cons, but imo DS2's cons far outweigh the pros. DS1's cons are at least confined to the end of the game, and it's DLC more than makes up for it...while DS2's cons pervade the entire game and its DLCs. (DS1 doesn't share a storyline with DS2, so don't feel pressured to play them in order or one at a time)

In DS2 they take control away from you by snapping your movement to angles, which is really annoying when combined with their decision to put an emphasis on platforming. They frequently resort to enemy spam, both as bosses and just around the world... Thrust attacks can't be aimed far enough up or down to hit small enemies without locking on, and locking onto them aims the camera so far down that it makes the horde encounters even more annoying... (Almost) the entire game is trivialized by giving you effectively infinite spammable heals early in the game. The animations don't have the same feeling of weight as DS1/3, as if you're not really making contact with the enemy (and vice versa). The world is basically just 5 linear paths from the hub area, and that's not necessarily a bad thing I guess but I do think it's less interesting than DS1's interwoven world. Your i-frames are tied to a stat you level up instead of your weight, which makes all "good builds" more homogeneous, and to add insult to injury they never even explain the stat to the player. The game has its upsides too, but these are my reasons for quitting after ~35 hours. Here is a more detailed review of the game.

For DS1: The game has a lot of issues after the first half. The Demon Ruins starts and ends with boss fights which are the only 2 fights in the game that I can comfortably call unfair. Tomb of the Giants is extremely dark and annoying to navigate even after you get the lantern. The Dukes Archives is great at first but the crystal caves are gimmicky and annoying, and it ends with an absolute pushover of a major boss. New Londo is by far the most annoying area, filled with enemies you can't hit without using a consumable (but you can run through the entire area pretty easily if you figure out where to go) and it ends with another gimmicky boss fight that severely punishes you for not doing enough damage fast enough. And all of these areas are required to go to the final boss, and tbh it's annoying enough just trying to remember how to get there when it's your first playthrough. While I could write 10x more about the good things about the game, this is already a long comment... but there's a reason DS1 earned its reputation as lightning in a bottle in spite of its late-game flaws.