Seems all of it was mentioned already so I'll sum it up:
- better and tighter story
- a higher variety of missions
- less guns but more distinctive (see Unreal Tournament, secondary fire and dual wielding would be huge)
- monster pattern variety (see Serious Sam)
- active skills, something that is actually noticeable would be nice
- an ending for christ sakes an ending
And if they find themselves with some extra time they could throw in a Claptrap companion (sorta like Wheatley) that would give you some extra cometary as you encounter a new interesting places, give some color and spice to the desolate land, even help you out on missions if you buy him new parts, or make fun of you, use voice synthesizers to speak your character name ... (whole sea of opportunity there)
- better and tighter story
- a higher variety of missions
- less guns but more distinctive (see Unreal Tournament, secondary fire and dual wielding would be huge)
- monster pattern variety (see Serious Sam)
- active skills, something that is actually noticeable would be nice
- an ending for christ sakes an ending
And if they find themselves with some extra time they could throw in a Claptrap companion (sorta like Wheatley) that would give you some extra cometary as you encounter a new interesting places, give some color and spice to the desolate land, even help you out on missions if you buy him new parts, or make fun of you, use voice synthesizers to speak your character name ... (whole sea of opportunity there)