When I first started the game I couldn't stand the fuzzy game font. Luckily you can quite easily change the fonts as well. Really helps with legibility.

My game resolution is set to 1360x768 on Win 10 running at 1080p.

For Civ4 no dlc the paths are:

Make a copy of this file before editing.

Civilization IV Complete\Civ4\Resource\Themes\Civ4\Civ4Theme_Common.thm

My changes in Civ4Theme_Common.thm start at line 371. Visual Studio Code is a good editor to make changes.

with SF_CtrlTheme_Civ4_Control_Font
{
// GFont .Size0_Normal = GFont("Fonts/segoeui.ttf", "Segoe UI Regular", "Regular", 10, GFlags(GFontFeature, GFC_FONT_ALPHA));
// GFont .Size0_Bold = GFont("Fonts/segoeuib.ttf", "Segoe UI Bold", "Bold", 10, GFlags(GFontFeature, GFC_FONT_ALPHA));
// GFont .Size0_Italic = GFont("Fonts/segoeuii.ttf", "Segoe UI Italic", "Italic", 10, GFlags(GFontFeature, GFC_FONT_ALPHA), 0, GRectMargin(1));
// GFont .Size0_BoldItalic = GFont("Fonts/segoeuiz.ttf", "Segoe UI Bold Italic", "Bold Italic", 10, GFlags(GFontFeature, GFC_FONT_ALPHA), 0, GRectMargin(1));

GFont .Size1_Normal = GFont("Fonts/segoeui.ttf", "Segoe UI Regular", "Regular", 16, GFlags(GFontFeature, GFC_FONT_ALPHA));
// GFont .Size1_Bold = GFont("Fonts/segoeuib.ttf", "Segoe UI Bold", "Bold", 12, GFlags(GFontFeature, GFC_FONT_ALPHA));
// GFont .Size1_Italic = GFont("Fonts/segoeuii.ttf", "Segoe UI Italic", "Italic", 12, GFlags(GFontFeature, GFC_FONT_ALPHA), 0, GRectMargin(1));
// GFont .Size1_BoldItalic = GFont("Fonts/segoeuiz.ttf", "Segoe UI Bold Italic", "Bold Italic", 12, GFlags(GFontFeature, GFC_FONT_ALPHA), 0, GRectMargin(1));

GFont .Size2_Normal = GFont("Fonts/segoeui.ttf", "Segoe UI Regular", "Regular", 17, GFlags(GFontFeature, GFC_FONT_ALPHA));
GFont .Size2_Bold = GFont("Fonts/segoeuib.ttf", "Segoe UI Bold", "Bold", 17, GFlags(GFontFeature, GFC_FONT_ALPHA));
GFont .Size2_Italic = GFont("Fonts/segoeuii.ttf", "Segoe UI Italic", "Italic", 17, GFlags(GFontFeature, GFC_FONT_ALPHA), 0, GRectMargin(1));
// GFont .Size2_BoldItalic = GFont("Fonts/segoeuiz.ttf", "Segoe UI Bold Italic", "Bold Italic", 17, GFlags(GFontFeature, GFC_FONT_ALPHA), 0, GRectMargin(1));

GFont .Size3_Normal = GFont("Fonts/segoeui.ttf", "Segoe UI Regular", "Regular", 18, GFlags(GFontFeature, GFC_FONT_ALPHA));
GFont .Size3_Bold = GFont("Fonts/segoeuib.ttf", "Segoe UI Bold", "Bold", 18, GFlags(GFontFeature, GFC_FONT_ALPHA));
// GFont .Size3_Italic = GFont("Fonts/segoeuii.ttf", "Segoe UI Italic", "Italic", 18, GFlags(GFontFeature, GFC_FONT_ALPHA), 0, GRectMargin(1));
// GFont .Size3_BoldItalic = GFont("Fonts/segoeuiz.ttf", "Segoe UI Bold Italic", "Bold Italic", 18, GFlags(GFontFeature, GFC_FONT_ALPHA), 0, GRectMargin(1));

GFont .Size4_Normal = GFont("Fonts/segoeui.ttf", "Segoe UI Regular", "Regular", 22, GFlags(GFontFeature, GFC_FONT_ALPHA));
GFont .Size4_Bold = GFont("Fonts/segoeuib.ttf", "Segoe UI Bold", "Bold", 22, GFlags(GFontFeature, GFC_FONT_ALPHA));
// GFont .Size4_Italic = GFont("Fonts/segoeuii.ttf", "Segoe UI Italic", "Italic", 22, GFlags(GFontFeature, GFC_FONT_ALPHA), 0, GRectMargin(1));
// GFont .Size4_BoldItalic = GFont("Fonts/segoeuiz.ttf", "Segoe UI Bold Italic", "Bold Italic", 22, GFlags(GFontFeature, GFC_FONT_ALPHA), 0, GRectMargin(1));
}

.Normal = SF_CtrlTheme_Civ4_Control_Font_Size3_Normal;
.Bold = SF_CtrlTheme_Civ4_Control_Font_Size3_Bold;
.Italic = SF_CtrlTheme_Civ4_Control_Font_Size3_Italic;
.BoldItalic = SF_CtrlTheme_Civ4_Control_Font_Size3_BoldItalic;

.Header = SF_CtrlTheme_Civ4_Control_Font_Size4_Normal;
.HeaderBold = SF_CtrlTheme_Civ4_Control_Font_Size4_Bold;

.Footer = SF_CtrlTheme_Civ4_Control_Font_Size1_Normal;
.FooterBold = SF_CtrlTheme_Civ4_Control_Font_Size1_Bold;

// .Fixed = GFont("Fonts/consola.ttf", "Consolas Regular", "Regular", 14, GFlags(GFontFeature, GFC_FONT_ALPHA));
// .FixedBold = GFont("Fonts/consolab.ttf", "Consolas Bold", "Bold", 14, GFlags(GFontFeature, GFC_FONT_ALPHA));

}