Here is a list of EAX effects per technology level for those interested. The fact remains that some games would utilize the effects to a higher extent them some others. EAX 5.0 is still relatively new and hasn't been as widely adopted for games yet. Future games may make better use of the technology. While some people love EAX in games others don't care about it so much. Depends on the type of games you play also.
EAX Level Feature List
EAX 1.0- Environmental Effect Presets
- 32 individual 3D voices
- Per-channel individual environmental presets
- Hardware DSP Rendering
EAX 2.0:- Occlusion Effects
- Material-specific reverb parameters
EAX 3.0:- 'Smoothing' between 3D audio environments
- Direct access to all reverb parameters
- Environmental Panning
- New reverb engine
- 64 simultaneous voices
- Beginning of the AdvancedHD Designation from new reverb engine
EAX 4.0:- Real-time hardware effects
- Multiple simultaneous environments
- Flange, echo, distortion, and ring modulation effects
EAX 5.0:- 128 simultaneous voices
- EAX Voice - Processing of microphone input signal
- EAX PurePath - EAX Sound effects can originate from one speaker only
- Environment FlexiFX - 4 available effects slots per channel
- EAX MacroFX - realistic positional effects at close range
- Environment Occlusion - Sound from adjacent environments can pass through walls