Does TD2 is really better than TD1?
Let's look on all possible aspects of both games. Years ago, I was sure, that TD2 is just the same as TD1. I still think like that: TD2 is the same as TD1, but improved and more casual.
World size
TD1 is winner here. Even with NYC added, TD2 has less space, than TD1 has.
World design
Nothing changed here - both games has very realistic environment. Just ones is winter and other is summer. Personally me like winter more alone, not even talking about Christmas decorations at green grass.
World activity
TD2 is clear winner here. TD1 basically has zero local events. From other side, TD2 has too much events going on sometimes.
Global events
Both games has it, but TD2 has more variety.
Game UI
TD2 is winner here. All UIs became much more user friendly, especially Inventory.
Game HUD
TD2 is winner here - at least, chat window is way better than it was in TD1. Still not perfect tho.
Gear variety
No doubt, TD2 is king. Just insane amount of possible gear sets and combinations.
Weapon variety
Mostly the same kinds of weapons, but with lowered amount of special abilities on them.
Exotics
TD1 is winner. While TD2 still has few really good exotics, most of them are just 'not worse than yellow' at best.
Gear and weapon crafting
TD2 has way better (casual?) crafting - most recipes are just known, with some exceptions, that you can just grind on CPs.
There was much less known recipes at start in TD1 and to learn new one - you should seek them at phoenix vendors.
Getting gear
It's way easier to get desired gear in the TD2 than it was in TD1: there is way less RNG in rolls and also Targeted loot system added.
Gear and weapon optimization
TD1 is winner - even after 75% discount patch, it's way too grindy to optimize gear in TD2
Resources
TD2 has tons of different resources, that is needed for crafting or optimization. From other side, just money played the role of most of them in the TD1, while money in TD2 is not important at all.
Modding gear and weapon
TD2 is more casual here. In TD1 you were need to craft mods for each weapon you gonna use and all mods have different stats and rolls.
Builds for newbies
TD2 is clear winner here. It's so easy to gather some needed pieces of gear, without breaking your mind with tons of requirements, which TD1 has
Builds for elders
TD1 is winner. Some classified TD1 sets are just stupidly OP, like Striker or Nomad. Also, there is more variety, not just copy-paste another hype-train YTer and be good.
Abilities
TD2 has more interesting active skills. But TD1 has passive skills and some of them were really good.
Apparel items
TD1 is clear winner here, even with fact, that you can recolor all gear pieces in the TD2, not just backpack, and change their appearance too.
Story content
Both games based on the same story and could offer pretty straightforward and short storyline. But TD2 also offered continue of the story with seasons.
Midgame content
Well, TD1 is winner here - there is just more activities to do, like Survival mode alone. Underground is not so boring as the Summit and Resistance is just endless (in difficulty also) fun. Missions are good made and both games are equal here.
Endgame content
Equal. DZ is DZ. Conflict is Last Stand. Both games has Legendary missions (TD1 has more of them) and Raids are improved version of Incursions. Personally me like Incursions more: less stupid mechanics and more actual shooting.
Combat AI
TD2 got improvements here. Yes, bots are still stupid, doing unlogical moves, but not as much as it was in TD1.
TD2 bots became more dangerous also - they do way more damage in general, than bots in TD1.
TD2 bots lost their sprint speed a bit and not able to dodge roll all day long anymore.
In the TD2 we actually started to get hit AFTER monsters made shot or popped above cover - do you remember TD1 grenadiers or snipers?
Shooting
This is personal part, but I like TD2 'gun feeling' more, than it was in TD1.
Character handling
Both games are pretty the same, but TD2 added more run speed to us: TD1 sprint was more like jogging, not actual sprinting.
Difficulty
TD2 has more difficulty layers than it was in TD1 and all of them are more difficult in general: TD1 challenging is easier than TD2 challenging, but TD2 also have extra Heroic before Legendary.
Artificial difficulty
TD2 got directives available everywhere, not just in the Underground. From other side, TD1 directives always has pros and cons for player, while TD2 ones are always downsides for player.
So, basically, TD2 became harder in combat and easier in looting than TD1.